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"It follows than as certain as that night succeeds the day, that without a decisive naval force we can do nothing definitive, and with it, everything honorable and glorious."

Ever since men have "gone down to the sea in their ships", they have also devised new and interesting ways of killing each other from these ships. The history of Naval Warfare can be split up into a number of distinct eras, based on the style of combat that the technology available at the time could support.

Galley Combat (Antiquity-1600s)

In this earliest period, ships were small, fragile, and mainly man-powered. Sail was a useful backup and a means of going longer distances but not very reliable or good for close in maneuvering. Because of this, the two main ways to win a fight at sea during this time were to ram the enemy to break his fragile ship, or to board his ship with soldiers and hack the rowers to pieces. Since the ships were made of wood, fire also made an effective weapon, but employing it without also setting your own ships on fire was tricky at best. Archers extended your range a little but didn't do enough damage to be decisive; you could always take cover behind the sides of the ship, and on larger ships the rowers were usually on a separate internal deck.

With the battles conducted close to shore and with lots of generally small, slow ships that were only useful at close range, tactics at sea in this period mimicked tactics on land. Your ships formed up into ranks, tried to maneuver and flank the enemy from the side, and then charged into them, with the battle devolving into a general melee after this point. If you want a good picture of this, the first act of Ben-Hur is a pretty decent reenactment.

Given the reliance on boarding, the front lines of ramming galleys were often backed by a fleet of whatever else happened to be available, because any ship that could carry additional men to the battle was potentially a warship. At this point in history the distinction been warships and merchant ships could be decidedly murky. This would remain true until the mid-1800s, when ships began to be made with more and more steel elements (eventually resulting in all-steel ships by 1900) and the internal layouts required to mount effective naval weapons began to differ significantly from those needed to efficiently carry cargo.note 

The ability for a merchant ship to function as (or disguise itself as) a light warship, and vice-versa, was an important part of the tactics of deception and ruse de guerre during this period and the subsequent Age of Sail. This was also one of the major reasons becoming a pirate was so easy until the mid-late 1800s; all you had to do was gather up a bunch of disreputable sailors, acquire a ship (which might have even come with weapons, as ironically, merchants would arm themselves in case of pirates), and prowl the usual merchant lanesnote . Indeed, some merchant vessels did a bit of opportunistic piracy on the side, British smuggler ships operating in the Castilian Caribbean being infamous for that sort of thing c.1650-1750.

It is something of a stereotype that galleys were largely manned by slaves at the oars but this was actually only true for a relatively short period from the 1500s to the mid-late 1700s in the Mediterranean and adjoining seas. Rowing a warship and maneuvering in order to effectively board or ram an enemy ship is actually quite difficult, and slaves are generally not highly motivated to fight the enemies of those who enslaved them, so ancient navies relied on free, skilled mariners, each handling a single oar and joining in the ship's defense if boarded, perhaps leavened by a modest (and thus controllable-by-the-free-crew) amount of slaves or freemen who had enough loyalty to the state and culture (often with promises of freedom) to be willing to go all out. note  It was only with the advent of naval guns that making huge portions of your crew galley slaves became viable, as the tricky maneuvering was no longer necessary; you just had to generally get the ship pointed at the enemy and let the gunners do their work. But of course, sailing vessels became dominant around the same time and so slave galleys quickly disappeared. The concept of a slave galley is so dominant in the popular imagination simply because they were used so much more recently and many more records and stories of their use still exist.

Naval battles of this period were generally epic in scope, because the small ships were relatively cheap to produce and most of the crew didn't need any skills other than the ability to pull an oar. The 480BC Battle of Salamis between an Athenian-led Greek Coalition and the Persian empire featured as many as a 1000 ships and who-knows how many men, and the 1571 Battle of Lepanto between the Castilian-Venetian Coalition and the Ottoman Empire involved 451 ships and sixty thousand men. Testament to the ease of replacement in these things is the way that despite losing nearly 4/5 of their entire fleet in the battle, the Ottomans managed to replace it within a year. The sailors and commanders with combat experience were another matter, of course.

Losses in these battles were made worse by the fact that most of the sailors didn't know how to swim, something which, strangely enough persisted well into the early 20th century: one theory held that teaching sailors how to swim merely encouraged them to abandon ship prematurely. Another was that sailors believed that during a shipwreck at sea, you were doomed anyway, and it was better to go with a quick death from drowning than a drawn out one from dehydration/starvation.

This period lasted until the mid-Renaissance period, when improvements in ship design and the invention of firearms led to a shift in strategy. The last great galley battle was the Battle of Lepanto in 1571, a Papal-Venetian-Spanish victory over superior Turkish forces that gives its name to a common strategy in Diplomacy.

The Age of Sail (1600s-1870s)

I wish to have no connection with any ship that does not sail fast; for I intend to go in harm's way.
John Paul Jones captain can do very wrong if he places his ship alongside that of the enemy.

Home to Wooden Ships and Iron Men, battles in this era were fought by large, tall-masted sailing ships packed to the brim with cannons firing iron shot. With stronger hulls and more efficient sails, ships now used sail power alone for propulsion, and could travel quite long distances, though not without risk. A good date to place the starting point of this phase in naval history would be the Battle of the Spanish Armada in 1588, resulting in an English victory over said Armada: while recognizable cannon-armed sailing ships had existed for almost a century by that point, unreliable gunnery and resistance to change meant that all previous battles had still turned on boarding actions and uncoordinated melees.

Cannons and maneuver were now the decisive weapons in battle — a ship or fleet with longer-range cannons and better maneuverability could dance around their enemy, just out of range of return fire, and pound them into a splintery, bloody mess. This is exactly what the English did to the Spanish in 1588. Battles took place at longer range, with fewer but more powerful ships. Tactics began to depart from the terminology of land battles and become unique to the ocean environment:

  • Since the vast majority of each ship's firepower was mounted on the side of the ship, standard practice for fleet battles was to get every ship in the fleet to follow one after after the other in a "Line of Battle", so each ship had a clear field of fire. Organizing many ships into a coherent line under sail power took significant effort and skill, and maneuvering was tricky at best, so once each side formed a line, usually they stayed in it all the way up to the point of contact with the enemy. This had the effect of making many fleet battles "boring", in the sense there was little maneuvering once battle was joined, just each ship blasting its opponent in the opposite line until one of them sank, was boarded and captured, or surrendered, repeating up and down the line until one fleet had enough. Correspondingly, admirals who did manage to use maneuver to their advantage were largely considered to be brilliant tactical geniuses.
    • The classic battle-winning maneuver was "crossing the T". Ships were heavily armed and relatively well armored on their sides, but very vulnerable from the bows and sterns, with relatively thin hulls, nearly no armament, and nothing to prevent a penetrating shot from flying clear from one end of the ship to the other. Thus, if you could sail your ships ahead or behind the enemy's line and cross their direction of travel at a right angle, your ships could fire full broadsides at the enemy's most vulnerable aspects while taking negligible damage in return. British Royal Navy Admiral Horatio Nelson famously achieved this against a combined Franco-Spanish fleet at the battle of Trafalgar in 1805, sailing his two lines perpendicular to the enemy line and cutting it in two places. During his approach, he basically crossed his own T, but once he cut their line, his two lines of ships were able to fire both left and right into enemy ships, essentially crossing their T four times simultaneously. Crossing the T would remain a relevant tactic into the age of big gun battleships—since even with turrets, most ships had more firepower on either side than to the front or rear—but lost favor with the advent of aircraft and submarines and remained obsolete in the missile age.
    • Another interesting fleet maneuver was "doubling". If your ships outnumbered the enemy and were able to maneuver, you could attack each enemy ship from both sides. Doing so again required a high degree of skill and coordination to avoid collision, friendly fire, or simply being carried out of range to support your allies.
  • Battles between single frigates could be more exciting because the ships were free to maneuver, and both captains would try to place their ship in the most advantageous position, ideally with your broadside facing their bow or stern. Often duels were decided by ruse or deception. The environment could also be a key factor; the side with a better knowledge of the local shoals and currents could often manipulate the other into running aground or being forced to break off the action, while fleet actions rarely took place in such treacherous waters as neither admiral would want to risk so many ships that way.
  • Since all ships were powered by sails, simply having "the Weather Gauge" (the upwind position) often made all the difference. The ship or fleet with the weather gauge had the initiative because its commander could choose whether they wanted to give battle (by sailing downwind to the enemy) or not (by staying upwind). Ships to leeward (downwind) could try to run away, but were not likely to be successful since the enemy had the same wind as them. Since working your way upwind was difficult, slow and subjected you to enemy fire the entire way, downwind ships were usually forced to accept whatever decision their opponent made on whether to fight or not. In some circumstances, having the weather gauge could even make your ships faster and literally (if you 'stole' their wind by being directly upwind of them) bring the enemy's to a standstill.
  • Despite their power, cannons were still relatively short ranged and were unlikely to sink or destroy a ship outright. A ship that lacked in the firepower department but had good maneuverability and lots of men could also manage to get in close and carry the ship by boarding. For this purpose, Marines were developed as soldiers specifically trained to fight at sea, as opposed to the crew just trying to kill the other crew. Ship designs gradually became more specialized as fleets gradually evolved from hastily organized mobs of armed merchant and trading vessels to professional standing navies.

Sea battles took on a decided "hurry up and wait" character during the Age of Sail, as ships were restricted to maneuvering with the wind and speeds rarely exceeded eight or nine knots. Warships could literally take hours maneuvering into a position where they could profitably employ their broadsides (the British approach at Trafalgar took almost all day). The desultory nature of combat under sail often meant sailors had to endure minutes or even hours waiting for a withering storm of fire that might decimate their ranks in seconds, only to spend minutes or hours waiting and preparing for it to happen again. Hence the expression "wooden ships and iron men."

It was this set of circumstances which caused the trope of The Captain to come about. When ships gained the ability to venture far from land and human contact, the Master or Captain of the ship had authority second only to God. With the warships of different states essentially similar in capability, and all at the mercy of the winds, it was the Captain's skill, leadership, and daring which most often won the day.

During this period the Dutch rose to rule the waves... and after four Anglo-Dutch Wars the British Empire replaced them, and from this we get most of our naval terminology in English. For example, the term Battleship comes from "ship of the line" or "line of battle ship", meaning a ship whose job is to form up with the fleet and battle the enemy in the "line of battle." They pretty much set The Laws and Customs of War on the sea during this period. This is also considered the "Golden Age" of international piracy.

The Age of Sail lasted roughly into the early 1800s, until sometime between the end of The Napoleonic Wars and the beginning of The American Civil War. By this point, most naval powers had consolidated their strength into two basic types of ship, the powerful "ship of the line" which sailed directly from home port to a massivenote  fleet battle, and the less powerful frigate, which could spend months or years at sea and generally fought other frigates in small squadrons (or even one-on-one battles) in sea lanes far from home.

Big Gun Battleships (1820s-1950s)

Fear God and Dread Nought.
Attributed to Queen Elizabeth I, as the inspiration for the name of HMS Dreadnought

There appears to be something wrong with our bloody ships today.
Admiral Sir David Beattie, Jutland

The mid nineteenth century brought with it a number of key advances in naval technology:

  • Explosive shells were developed for naval guns, greatly increasing their destructive power.
  • Improvements in gun design increased range, weight of projectiles, accuracy, and rate of fire. Fewer but bigger guns became the norm.
  • New mechanical recoil, reloading, aiming, and fire-control systems allowed guns to be placed in turrets able to point in any direction. Naval gunners could now hit targets at range even on pitching seas, and ship designers were freed from having to place all the guns on the sides of the ship.
  • The steam engine freed ships from dependence upon the wind, and screw propellers soon replaced inefficient and vulnerable paddle wheels.
  • As a reaction to the above technologies armor plating was fitted to warships (first seen in the Crimean War and widely employed in the American Civil War).
  • And later, ships began to be built entirely of iron and later steel.

The Koreans were probably the first to armor ships with ironnote , using them to defeat a Japanese invasion in the late 16th century, but news of this success never reached the wider world, and the amount of armor that could be carried on any ship powered by sails or oars was limited; a truly successful seagoing armored ship requires an engine of some sort.

Steam and Sail (1810s-1870s)

Steam-powered paddleboats began appearing in the first decades of the 19th Century, and stern-wheel paddleboats especially proved useful for riverboats and other watercraft traveling short distances over calm waters. While a oceangoing steamships utilizing paddle propulsion were developed starting in the 1810s. Unlike the riverboats, blue-water vessels tended to work better with side-mounted paddle wheels. These gave a ship exceptional low-speed maneuverability, but they were not exactly gamebreakers as the paddlewheel interfered with the placement of guns, and presented a large target to enemy fire. Attempts to enclose the sidewheels inside an armored box did more to reduce stability. The development of the screw propeller in 1840s - which solved the earlier problems along with greatly increasing efficiency - quickly made steam-and-sail ships practical and led to a number of screw frigates.

Ironclads (1850s-1890s)

To some degree, development of the ironclad (wooden-hulled ships encased in iron armor, as opposed to complete iron hulls) came from the French Navy attempting to use technology to offset the numerical superiority of the English Navy. The French built the (unarmored) 90-gun steam-powered line-of-battle ship Napoleon in 1850, and several French-designed ironclad floating batteries were fielded in the Crimean War. Putting the two together, the French commissioned Gloire in 1859, an oceangoing 36-gun ironclad that would easily lay waste to the unarmored Royal Navy. The British countered with HMS Warrior in 1860, the first iron-hulled warship.

Numerous armored gunboats appeared during the US Civil War, mostly designed with broadside batteries and mostly intended for inshore/riverine operations. USS Monitor introduced the rotating armored gun turret, allowing the gunboat to engage targets from any angle (the arrangement was so peculiar at the time that observers initially called the turret a "cheesebox" because that's what it looked likenote ), she was also iron-hulled (less than two years after Warrior) and, lacking masts or rigging of any kind, entirely reliant on her steam engines—a rarity at that time. In 1862, the first battle between ironclads took place, with Monitor engaging CSS Virginia after the latter had attacked a Union blockade of Hampton Roads, Virginia and damaged or destroyed several ships. The two ships fought to a draw, neither having the firepower to significantly damage the other. With this proof that a single ironclad could wipe out an entire unarmored fleet and that nothing could stop it but another ironclad, Great Britain and France decided that ironclads were no longer simply a supplement to their mostly unarmored fleet - ironclads were now the only type of warship worth building. Construction of unarmored line-of-battleships ended almost immediately.

The 1866 Battle of Lissa, a fleet battle between Austria and Italy including both unarmored and ironclad frigates, took place at a time when it was possible to armor a ship such that no common naval gun could defeat it. Many naval experts took from this the belief ramming was a critical tactic against ironclads, because of course any armored ship would naturally be invincible to guns.note 

As the weight of the steam engine, heavy guns, and armor only allowed for ships of a single gun deck, ironclads were almost all single-gun-deck ships and appropriately referred to as "armored frigates" from around the 1860s-1870s. As First- and second-rate multi-gun-deck ships-of-the-line were no match for these fifth- and sixth-rate warships, the Royal Navy's rating system was no longer a meaningful expression of a particular warship's capabilities. By the 1870s, the rating system was tossed out and these new warships were classified as "cruisers."

Armored warships continued to be constructed of a combination of iron and wood until the development of steel shipbuilding in the 1870s. Armor technology improved and guns became increasingly powerful. With the profusion of new ammunition types—Armor Piercing, High Explosive, Cannister, Illumination, and so on—the way that guns were described changed. Where sailing warships carried cannon that threw balls of specific weights (9-pound, 12-pound, 24-pound, etc.), the new generation of naval guns were described in terms of the barrel diameter: 6-inch, 9-inch, 12-inch, etc. Marine steam power was sufficiently reliable, and (more importantly) coal fueling stations became sufficiently numerous, that sails largely disappearednote , although masts were retained because they were useful for signalling, fire control, and so forth.

Warship development became rapid and confusing; many countries repeatedly designed and laid down ships that would become obsolete before they were even completed, and a total lack of combat experience led to some decidedly daft ideas in shipbuilding. In the last decades of the 19th Century, cruisers began being classified based on their thickness and arrangement of armor - unprotected cruisers (no armor), protected cruisers (internal armored deck but no side armor), and armored cruisers (internal armored deck and side armor). In 1892 the Royal Navy formally classified its most powerful steel warships as "battleships."note 

Pre-Dreadnought Battleships and Cruisers (1890s-1910s)

The line between ironclad and battleship is not clear, but arguably the first battleships were the turreted, sail-less ironclads of the 1870s - HMS Devastation commissioned in 1871, the all-steel French Redoubtable of 1878, and the Italian Caio Duilio of 1880. By the 1890s most capital ships were of a similar type — coal-powered triple-expansion engines, heavy steel armour, with a main armament of around 4x 12 inchnote  guns (usually two each in turrets before and after the superstructure), an intermediate armament of around 10x 5-to-8 inchnote  guns (in turrets or broadside casemates), and a secondary armament of 10-30 3-to-5 inchnote  guns (turrets or casemates). The main armament was powerful but slow-firing, meant to punch through heavy armour with ease; the secondary armament was quick-firing but weak, meant to wreck the lightly armoured parts of the target with a torrent of explosive shells as well as destroy lighter vessels; the intermediate guns split the difference.

In all cases, the entire armament was expected to work together attacking a single target at a relatively short range — although the bigger guns could shoot further, the fire control of the period was too primitive to allow for accurate long-range shots. Likewise, the line between cruisers and battleships was blurry, since the battleship was initially no more than a more powerful type of cruiser. As technology slowed enough for standard ship roles to start developing, it became typical for the cruiser to become a fast, long-range ship with around 8 to 12 guns in the 5-to-10 inch note  range. The idea is that a major navy would do most of its commerce raiding and Gunboat Diplomacy with a fleet of cruisers, and keep the battleships for fleet actions against the battleship fleets of other navies — similar to the roles of frigates and ships-of-the-line during the Age of Sail.

This was around the time the United States — having been predominantly a frigate navy for its entire historynote  — began to build itself into a significant naval power. In response to Brazil's launching of the battleship Riachuelo in 1883 (which by itself made Brazil the most powerful Navy in the Americas by a wide margin), the US Navy launched the battleship USS Texas and her half-sister, the "Second-Class Battleship" (often considered an armored cruiser with bigger guns than usual) Maine.note 

In the Spanish-American War (1898), the new all-steel ships of the U.S. Navy sank two Spanish fleets and seized their Caribbean and Pacific colonies without losing any ships of their own,note  despite admittedly poor gunnery—the Americans missed most shots, while the Spanish couldn't hit anything. The only damage the American ships received in battle was when the blast from Texas's main battery blew holes in her own superstructure. In the Russo-Japanese War (1904-05) (opened with a surprise torpedo attack against the Russian fleet in Dalian/'Port Arthur', Liaoning province) the Imperial Japanese managed to sink Imperial Russia's (smaller-than-Japan's) Pacific Fleet with land-based artillery and destroy Russia's (slightly-larger-than-Japan's) Baltic fleet, the latter in less than an hour.

The torpedonote , originally meant as a short-range weapon for battleships and cruisers, was quickly realized as a very mobile weapon that could be carried by vehicles that couldn't possibly carry a heavy gun. Countries that couldn't afford battleships quickly adapted the torpedo to smaller craft such as torpedo boats and (eventually) submarines — very inexpensive vessels that could easily sneak up on an unsuspecting battleship and sink it. Torpedo boats were further divided into "fleet" torpedo boats capable (somewhat) of blue-water operations on the high seas, and the smaller and faster "motor torpedo boats" or "PT boats" that stayed closer to shore. This in turn lead the big navies to develop "Torpedo Boat Destroyers;" fast, maneuverable ships able to keep up with torpedo boats and carrying enough guns to readily overpower them before they could do any damage. In response, fleet torpedo boats got bigger and mounted more guns, while torpedo boat destroyers soon mounted torpedo tubes in case they got a chance to sucker-punch an enemy capital ship. The two types soon merged, and "torpedo boat" was dropped from the name, giving us the modern Destroyernote . Thus, shortly before World War I, the Types of Naval Ships had been well-developed — the battleship, the cruiser, the destroyer, the submarine, and the torpedo boat.

Dreadnoughts, Super-Dreadnoughts, Battlecruisers, and Fast Battleships (1900s-1950s)

By the turn of the 20th Century, the Royal Navy had made several important observations about battleship engagements in the 1890s and early 1900s, particularly the Russo-Japanese war mentioned before. First, speed was an undervalued asset - the faster fleet can control of many important aspects of battle. (Whether or not to engage, what range to fight at, etc.) Second, the effective range of even pre-existing naval guns was quite a lot larger than expected - the Russian and Japanese fire directors at the Battle of the Yellow Sea maxed out at 4 and 6 km, respectively, and yet they each made solid hits at distances up to 13 km. Additionally, longer-range torpedoes made it too dangerous for battleships to fight closer than 4 km. Both of these trends seemed likely to continue. At these ranges, however, all but the main batteries were minimally effective. Further, the Battle of Tsushima aptly demonstrated the value of the new wireless telegraph, as Japanese scouts were able to immediately notify the Japanese fleet when the Russians were spotted, allowing them to quickly respond at the place of their choosing.

The British, in a brilliant case of "Adaptation Distillation", decided to leapfrog everyone by combining all of these technological advances into one battleship. For speed, she eschewed triple-expansion steam engines for more powerful steam turbinesnote . For protection, heavy armor around her machinery, magazines, and gun turrets, with minimal armor around non-critical spaces.note  For firepower, no intermediate guns at all, only ten 12" guns in 5 independent turrets.note  They named her HMS Dreadnought and she reduced the worldwide number of first-class capital ships to 1, as no one else had anything that could compete. But the British technological lead was only temporary, as Germany, the U.S., and Japan all had Dreadnought-style battleships on the drawing board before she was even launched (and in some cases before her keel was laid.)note  Clearly the all big gun battleships' time had arrived and dreadnought construction became the first 20th century arms race. The US Navy soon one-upped Dreadnought with USS South Carolina. Although slower and shorter-ranged, she introduced the "superfiring" gun layout, with the second gun turret sitting on an elevated mount to fire over the top of the first, maximizing their field of fire and allowing South Carolina to match Dreadnought's throw weight with fewer guns at less cost. All future designs would adopt the best features of both ships.

During this time the idea of a hybrid warship that combined the speed of a cruiser with the fire power of a battleship was appealing to some admirals, particularly Britain's Jackie Fishernote , and resulted in the development of the battlecruiser. By sacrificing armor protection, it was believed these ships were able to outrun anything that could sink them and out-gun anything that could catch them, much like the heavy frigates of the age of sail. Problem is that unlike frigates of old, the cost of building and operating such ships often matched (and in some cases, exceeded) that of regular dreadnoughts, which made them exceedingly inefficient for their intended role. Furthermore, no admiral could resist the temptation to use the battlecruisers' big guns to pad his fleet's salvo weight, and this would spell almost certain doom for the fragile battlecruisers that were never intended to face full-on battleships in line-on-line fight.

The dreadnought increased the range at which battles could be fought to approximately eleven miles or all the way out to the visible horizon and the advent of radar in WWII extended these ranges even further. The German Scharnhorst hit the aircraft carrier HMS Glorious, and in a separate battle HMS Warspite achieved a hit on the Italian battleship Giulio Cesare, both at about at 25,000-26,000 yards (15 miles).note  USS Iowa straddled Japanese destroyer Nowaki with five out of ten salvos at 35,000-38,000 yards (20 miles) note  and USS White Plains received a damaging near miss at 32,000-33,000 yards (19 miles)note  when a salvo of 18.1 inchnote  shells from Yamato exploded under her bilge. Dreadnought battleships and the counters developed against them created the Types of Naval Ships that we use today. Tactics no longer resembled land warfare in the slightest, focusing instead on good scouting so you could discover the enemy first and place your own battleships in the most advantageous position.

Ten years of dreadnought battleship development were finally put to the test of massed combat during the Battle of Jutland on 31 May 1916, the British Grand Fleet confronted the German High Seas Fleet off the coast of Denmark. The battle itself was inconclusive: the British lost more ships and men but more of the German ships were damaged. However, the British Grand Fleet was larger and could afford to take losses whereas the German High Seas Fleet could not; the Grand Fleet was ready for battle the next day and the High Seas Fleet wasn't. Here the battlecruiser concept died rather spectacularly with the loss of HMS Queen Mary, HMS Indefatigable, and HMS Invincible in catastrophic explosions; Admiral Beattie's own flagship HMS Lion only avoided sharing their fate by the narrowest of margins due to a Heroic Sacrifice by a turret officer, prompting Beattie's acerbic quote abovenote .

On the German side SMS Lutzow was scuttled after the battle, too severely damaged to make port and SMS Seydlitz only barely managed to limp home with less than one foot of freeboard minus all of her turrets. All but Lutzow were sunk by other battle cruisers and no battle cruiser on either side returned undamaged. None of the more heavily armored Dreadnoughts were sunk. Though some battlecruisers survived until WW2 few were built during the interwar period. During WW2 battlecruisers fought battleships on 3 occasions:note  each time, a battlecruiser was sunk. Jutland also saw the introduction of a new kind of super-dreadnought in the Queen Elizabeth class, which attempted to address the battlecruisers' shortcomings by combining relatively high speed with even bigger guns and commensurate protection.

After Jutland, the Royal Navy remained in control of the North Sea and maintained their Naval Blockade of Germany. The Germans never challenged the Royal Navy again. After a (heavily biased, with egregious methodological and computational errors) study claimed that 'unrestricted' (indiscriminate) anti-commerce submarine warfare could cripple the Entente's war effort the Reichstag went along with the recommendations of the Navy and OHL (Army High Command, headed by Hindenburg and Ludendorf) and voted in favour of it in early 1917. This ultimately and predictably, not least by Chancellor Bethman Hollweg, backfired when it drew the United States decisively into the war against them (when combined with the blundering of the independently-acting diplomatic service, which tried to persuade Mexico to attack the USA). The powerful, if untested, US Navy added its battleships and cruisers to the Home Fleet under British commandnote , turning the prospect of another German breakout attempt from a desperate long shot to certain suicide. Having no further role to play in the war, the High Seas Fleet was neglected. The sailors on larger vessels were confined to port, suffering from reduced rations and subjected to harsh discipline. The last straw came in 1918: the German admiralty, knowing that the war was all but lost, decided to send out the fleet for a last, glorious (and completely futile) action. This led the sailors of the High Seas Fleet to mutiny, hastening the collapse of the German war effort. The German fleet eventually scuttled itself at the British anchorage at Scapa Flow on June 21, 1919: 52 ships were scuttled in all, including 10 battleships and 5 battlecruisers.

Despite the ambiguous and much debated results of Jutland, a new round of battleship construction was triggered, as each nation sought to acquire "super-dreadnoughts" featuring ever higher speeds with even heavier armor and bigger guns. The high costs of this naval arms race grew to be such a concern that the world's first major international arms reduction treaties (The 1922 Washington and 1930 London Naval Conferences) were aimed at limiting battleship size and reducing their numbers. (Ironically, Japanese anger at the way they were treated at these conferences actually helped set the stage for World War II). As these treaties were eventually abandoned during the run-up to World War Two, the super-dreadnought gave way in the American, British, French, Italian, and German navies to the fast battleship: ridiculously large and powerful with more powerful engines and better hull design that allowed these new heavy hitters to reach the same speeds as cruisers, while also keeping their fuel consumption low enough to greatly extend their operational range over that of the dreadnoughts and super-dreadnoughts. The fastest, the U.S. Iowa class, could cross the ocean at 33 knots, and is considered the ultimate development of the fast battleship.

The Japanese chose a different route: building the largest battleships ever created, by a wide margin. Yamato and her sister Musashi had nine 18.1-inch guns each, with tremendously-thick armor and a small army's worth of secondary, intermediatenote , and antiaircraft guns.note  How these "superbattleships" would have performed against the American Iowa and British King George V-class fast battleships is a topic of speculation, as both of them were sunk by American aircraft (though it wasn't easy)

The pace of combat accelerated considerably over each of these periods, as each new advance in technology allowed ships to travel and fire farther and faster. Steam power freed ships from from dependence upon the winds, though it did not free them completely from the affects of the sea (one reason Bismarck fared so poorly in her final battle was her loss of steering left her crew unable to plot a course that would minimize the effect of the waves on their gunnery.) Breech loading guns replaced muzzle loaders, turrets replaced manual training, gun directors replaced manual aiming, rates of fire increased. Maneuvers that took hours under sail now took only minutes, and high rates of fire meant a battle could be over in seconds if the enemy found your range. A single well-aimed salvo from Bismarck totally destroyed HMS Hood, and when the Japanese destroyer Amatsukaze attracted the attention of USS Helena at the Naval battle of Guadalcanal when her captain left his searchlights on too long she was riddled by 20-30 hits and near misses in just over a minute and a half, only surviving because the burning USS San Francisco obstructed Helena's line of fire.

Development of naval aviation initially strengthened the role of the battleship by allowing small floatplanes to act as scouts and artillery spotters, but as aircraft technology advanced their attack capabilities eventually made the battleship irrelevant. WWII was the last hurrah for the battleship; development of aircraft carriers quickly pushed battleships into a supporting role during the conflict, and by the end of the 1940s the battleship had been replaced as the primary instrument of sea power.

That being said, there was some use of battleships post-war. The Iowas were reactivated and modernized several times during the Cold War, mainly for the Naval Gunfire Support mission, but also for their capability as surface combatants. Additionally, the Bikini Atoll tests proved that an armored battleship is the most survivable ship in a nuclear environment (surviving anything short of a direct hit or underwater near-miss, and keeping the crew alive), and air conditioning and filtration systems could protect the crew from fallout. Their high speed (faster than most of the Soviet fleet) and ability to continue fighting at visual range with EMP-proof analog fire control systems meant that a fast battleship was at least situationally formidable. However, they never had any anti-submarine defense beyond just the ability to absorb more torpedo damage than the average ship, and their air defenses against jet aircraft and cruise missiles were last-ditch at best.

Carrier Aviation (1920s-present)

[T]he torpedoplane, under favorable conditions, would make the $20,000 airplane a worthy match for a $20,000,000 battle cruiser.
Rear Admiral Bradley A. Fiske, 1917

US Navy Telegram, 7 December 1941.

The airplane was invented just before WW1 and almost immediately afterward someone thought "Wouldn't it be cool if we could use these things to spot enemy ships?" which quickly morphed into "Wouldn't it be really cool if we could use these things to blow up those ships?" and "wouldn't it also be be cool if we could get these things across oceans without having to fly them the whole way!"

Thus Naval Aviation was born. At first they were just little seaplanes used as long-range scouts for Battleships, but as airplanes developed they gradually became capable of carrying enough explosives to do some major damage. Meanwhile, the desire for scouting aircraft to accompany the battle fleet beyond the range of land based aircraft resulted in an entirely new type of warship when the Royal Navy converted HMS Furious into the world's first aircraft carrier. This was followed by a two-decade period of naval experimentation similar to the one proceeding the Big-gun battleship that also produced some rather odd-looking vessels before arriving at the basic carrier design of a large fast ship with a flat deck and minimal superstructure that is still familiar today. And to pile irony upon irony, several of these carriers were built using the hulls of battleships and battlecruisers countries were forced to discard under the Washington Naval Treaty.

In the inter-war period there was a huge debate in the world's navies between proponents of building more battleships and supporters of building more aircraft and carriers. The battleship side argued that aircraft were fragile, unreliable, too dependent upon good weather, couldn't carry enough stuff to damage a battleship and thus were a waste of money. The carrier side argued that superior range and speed would enable their airplanes to locate, attack and sink any enemy battleship before it even came into gun range and since carriers could better defend themselves against enemy aircraft and the airplanes themselves were relatively cheap and could be built in vast numbers that meant battleships were a waste of money.

Meanwhile advocates of land-based air power such as Colonel Billy Mitchell of the United States Army "agreed" with both sides by arguing that aircraft made the entire idea of a Navy obsolete and thus all warships were a waste of money that (incidentally) should be given to the Army to buy more bombers. (If sailors on both sides of the battleship/carrier debate agreed on one thing it was a common hatred for "army pukes" like Mitchell.) However, while Naval Aviation in the 1920s and 30s clearly showed some future promise, it did not yet demonstrate the sort of clear superiority that would make Admirals willing to give up their battleships. Air forces on the other hand spent much of the 1930s developing fast, long-range twin-engine torpedo bombers for coastal defense.note 

Parallels could be drawn between the torpedo and naval mine — cheap weapons capable of damaging or destroying a battleship, deliverable by inexpensive vehicles (torpedo boats, destroyers, submarines, or minelayers) which introduced new dynamics to naval warfare in the first decade of the 20th century, but failed to knock the battleship off its pedestal. Surely airpower would likewise be inconsequential so long as battleships mounted a couple anti-arcraft guns and applied appropriate defensive tactics.

A series of naval airstrikes over 1940-41 quickly made clear the battleship was on its way out, and control of the sea rested on who could throw the most aircraft at whom:

  • On 11-12 November 1940 a daring British nighttime carrier strike at Taranto severely damaged three of the newest battleships in the Italian fleet, using a few obsolete and underarmed torpedo bombers.
  • On 26 May 1941 another British carrier strike (flown by inexperienced pilots in appalling weather conditions, with the aforementioned planes) managed to achieve a lucky torpedo hit that disabled the steering on the German battleship Bismarck, preventing her from fleeing the pursuit of a British battleship force and leading directly to her sinking/scuttling.
  • On 7 December 1941 Japan combined all six of its fleet carriers into a unified strike force and surprised the US Pacific fleet at Pearl Harbor, destroying virtually all of their aircraft on the ground and disabling or destroying seven of the eight battleships present, along with a number of cruisers, destroyers, auxiliary ships, and port equipment.note 
  • On 10 December 1941, HMS Prince of Wales and HMS Repulse (a brand-new battleship and an old battle cruiser, respectively) were engaged by aircraft off Malaya. Despite being out at sea, fully alert and defending themselves (but without friendly fighter cover) the ships were no match against a concerted aerial attack by Japanese land-based torpedo bombers note . It is also worth noting that sea conditions during the attack meant a significant number of torpedos missed the main armour belts, showing another weakness of traditional sea-power.

Tactics changed again, from "take your fleet and find the enemy's and sink it with your battleships" to "find the enemy's fleet with your planes and sink their carriers while protecting your own at all costs" and all surface ships besides carriers became little more than escorts. Battle ranges increased yet again, this time to well over the horizon, and battles were fought entirely with aircraft without each fleet ever seeing the other. The Old-School Dogfight as a factor in naval warfare originates here, though it took the invention and proliferation of radar to make fleet defense from air attack possible. Ironically, the heavy bombers that Mitchell believed would make navies obsolete proved largely ineffective at attacking ships. Some significant changes were seen:

  • Line formations and "crossing the T" make little sense when exchanging airstrikes since attack could come from any direction more quickly than a fleet could maneuver. Instead, circular formations that put layers of escorts armed with anti-aircraft weapons in a "ring of steel" around the high-value ships became dominant. Conveniently this approach also worked decently well at defending against submarine attack.
  • Planes could be used to provide an outer ring of defense for surface units at one extreme or be committed to all-out, nothing-held-back "alpha strikes" at the other, and everything in between.
    • Efficient air direction became very important, especially as WWII wore on and more ships and aircraft began carrying radios and radars. The side that could more effectively detect their enemy, marshal planes to intercept or attack, and react to changing circumstances had a major advantage. The ability to fuse information from dozens of sources into a single coherent picture became increasingly important.
    • One interesting strike maneuver was "shuttle bombing". If a carrier group found a target that was within range of both their own planes, and a land base, a mission could be planned so that the attack aircraft could strike their targets twice in rapid succession: once flying from the carrier to the land base, and again on the way back from the land base to the carrier.
  • Fleet maneuvers and routine now needed to be planned around flight operations.
    • Night maneuvers were now scheduled to give pilots the best possible opportunity to find and attack their targets at dawn, or to evade an enemy trying to do the same.
    • The direction a fleet steamed had to be managed to ensure both that the planes would be in range of their targets, but there would also be good wind for launch and recovery, and sometimes these objectives were contradictory. For example, sometimes the wind demanded the fleet steam away from the enemy in order to launch or recover aircraft, leaving a very narrow window for executing a strike.
    • All maneuvers once the planes were launched had to be planned so that the carriers remained in range to recover returning aircraft.
    • Ships, aircraft, and techniques began to be optimized to increase "sortie rate", or the speed with which an airstrike could be launched, carry out their strike, be recovered, reloaded and refueled, and launched again.

Meanwhile, acquiring new carriers became so important that the U.S. converted nine cruisers under construction into "light" carriers — almost anything would do as long as it could launch planes. The U.S. also constructed or converted dozens of small "escort" carriers that the U.S. and Royal navies used for escorting convoys, antisubmarine patrols, and invasion support — nearly a hundred carriers all told.

Five (arguably six) battles between carrier groups involving the mutual exchange of air strikes took place during World War Two, most famously Midway in June 1942. note  All of these battles took place in the Pacific between the U.S. and the Japanese. By the end of the war the U.S. Navy's Pacific fleet outnumbered all of the rest of the world's navies put together, centered around massive task forces composed of dozens of carriers plus all the logistics necessary to support them across transoceanic distances. By contrast the 21 major Pacific surface engagements (most of which took place in the South Pacific at night) generally proved less decisive though costly in men and materials, with the sole exception of the battleship era's second to last hurrah, the horrific Second Naval Battle of Guadalcanal on 14-15 November 1943.

All of the carrier battles took place in the Pacific since only the US, Japan, and Great Britain were able to create naval air arms. The Germans belatedly realized the value of carriers in 1940 but were never able to complete any (they never even developed a naval air arm as Hermann Goering saw it as a threat to his authority as Commander of the Luftwaffe). France had a single operational carrier, which spent the war interned at Martinique after France's armistice with Germany. The other major sea power, Italy, had little need for carriers since they operated mostly within the Mediterranean well within the range of land-based aircraft. (That no other country could even be considered a major sea power indicates just how expensive navies had become.) With the Italians bottled up in the Mediterranean and the German surface fleet largely confined to Norway and the Baltic most carrier operations in the Atlantic consisted of convoy escort and anti-submarine warfare with attacks on German warships in port and a little invasion support thrown in.

The old methods had their last hurrah in World War II as well, largely because there were still conditions (night battles and rough arctic seas) where aircraft were ineffective, especially early in the war; as well, even the late-war US Navy aerial strikes had issues stopping a large, determined surface force willing to take casualties (see Sibuyan Sea), and while carriers could easily evade battleships, landing forces and supply ships were another story, requiring battleships to hang around a bit longer. There were nine battleship-on-battleship engagements in WW2, all but one happening by 1943. note . There were also many surface engagements among cruisers and destroyers in the Mediterranean, Pacific, and Indian oceans without battleships present. And battleships did continue to prove useful since they made good antiaircraft and shore bombardment platforms. Later they were even placed in front of the carriers to protect them from aircraft attack since they could take more damage and were more expendable in the aviation era and proved highly effective in this role since late war advances in radar and anti-aircraft gunnery gave them the means to protect themselves if they were provided with sufficient air cover.

There were also two engagements of where battleships managed to get within gun range of carriers. The first (HMS Glorious vs KM Scharnhorst and Gneisenau) took place in 1940 and was won by the battleships; the second (the Battle Off Samar) took place in 1945 and was won by the carriers. But by 1945 battleships were no longer a match for even escort carriers. The swan song of the battleship was written in the final, futile sortie of IJN Yamato, which was literally obliterated by swarms of aircraft less than halfway to her objective, having never justified the vast resources expended on her construction. Barely one month later the last operational major Japanese warship, the heavy cruiser Haguro, was sunk off Penang by a British destroyer squadron in the world's last mass torpedo attack. Ironically, the navy that launched the era of seaborne air power suffered its final defeat in history's last traditional surface battle.

This period of warfare is more or less still going, with some modifications as seen below.

Submarine Warfare (1910s-present)

Take her down!
The last known words of Commander Howard Gilmore, Captain of USS Growler (SS-215). Wounded during a surface gun battle with a Japanese escort vessel Gilmore ordered his crew to dive while he was still on top of the submarine and outside the pressure hull, sacrificing his own life to save the ship.

The only thing I truly feared during the war was Dönitz and his U-boats.

The very idea of a ship has a single weak point: if it sinks, it's useless. Someone finally got to the conclusion "Gee, wouldn't it be funny if I swam over there and made a hole in that ship?". Not everyone, though, is a good swimmer, and not every good swimmer swims well enough. So someone came up with the idea that all this swimming under sea's surface can be done by a dedicated machine: sub(under) marine(sea); in a sense, it's a SUBversion of the concept of a ship.

Naturally, it's an idea that has primarily appealed to underdogs. Which is why the first recorded instances of attempted submarine attacks were made by weak naval powers against much stronger ones. The first recorded attempted submarine attack took place in the American Revolutionary war, when David Bushnell's Turtle (essentially a wooden barrel driven by hand-cranked propellers) tried and failed to attach a mine to a British warship. The second, more successful attack occurred during the American Civil War when the somewhat more sophisticated (but still hand cranked) Confederate submarine Hunley managed to sink U.S.S. Housatonic with a "spar torpedo" (essentially a bomb on a stick) at the cost of the lives of her own crew. The Confederates also tried steam powered semi-submersibles called "Davids" that were virtually submarines (only a small part stuck up above the water) but without success.

Two things were invented near the end of the 19th Century that made things look up (or down) for submarine enthusiasts: the first was the invention of the self propelled or "locomotive" torpedo, which gave submarines a weapon they could use from a range greater than 20 feet and without surfacing, and the second was the invention of the internal combustion engine and the electric motor, which together freed submarine crewmen from all of that laborious hand-crankery provided they were given sufficient time between dives to recharge their batteries on the surface. Once again it was a couple of Americans, Simon Lake and John Philip Holland,note  who put these things together to create the first modern submarines, though since the U.S. was no longer a naval underdog Lake and Holland (who were competitors, not collaborators) had to go elsewhere to find someone who was truly interested in their machines.

And now we come to the part when it begins to matter, because for Lake in particular that someone was Wilhelm II, the Kaiser (Emperor) of Germany (Lake's main competitor Holland, on the other hand, had his main success with the Germany's main rivals United Kingdom and Imperial Russia). Germany, being unified only around the 1870s, was a bit late to the colonial cake. Being late, it had yet to build up its naval muscle. The Germans took up the development of their Hochseeflotte and, through creating it and pursuing a ham-fisted policy of colonial expansion to match everyone else's, help drive a neutral country (the insular United Kingdom) into the arms of its enemy (France). A country which was renowned for its naval capabilities, to boot. Between this and the failure to maintain cordial relations with Russia, which France also drew into her orbit as an ally, Germany had surrounded herself with strong enemies and just one weak friend (Austria-Hungary).

However, the German navy noted, the situation might not be as grim as it appeared. Germany was dependent on foreign trade, but so was France. Britain was even more so. While trade ships could be protected from surface ships by the Entente's navy, they would still be vulnerable to submarine attack. Even from the submarines of the day, which were still little more then temporarily submersible (one hoped) torpedo boats. A bit of trivia: one of the most successful submarine captains of World War I was an Austro-Hungrian officer named Georg Von Trapp.

And thus, the Germans embraced the submarine as a means of naval warfare, and thus the word U-Boat (Unterseeboot, "undersea boat" — or "sub"-"marine") entered dictionaries, with all submarines being referred to as "boats" to this day. While the Germans were generally quite gentlemanly surfacing to stop ships before torpedoing them their superiors eventually realized that this exposed their subs to British countermeasures and in early 1917 high command ordered them to stop doing it as it threw away the advantage of surprise. Besides, depriving France and Britain of sea trade required more than just torpedoing merchant vessels, so the idea of unrestricted submarine warfare was born: sink all ships you suspected of aiding your enemy, even if they belonged to neutral states, and let the chips fall where they may.

Unsurprisingly, the 'study' which 'proved' that adoption of such a policy could win the war for Germany was championed by the third OHL despite there being no grounds to believe it would work. Germany's situation appeared truly dire at the time, with Russia standing firm in the east and the USA's sales to the western Entente increasing daily. Unrestricted Submarine Warfare was the only policy which promised victory, however unlikely some thought it might be (and rightly). The motion was voted through with overwhelming cross-party support from virtually the entire Reichstag.

The policy not only failed, but drew the United States into the conflict in mid-1917. This was not an immediate disaster, as the USA had a very small army at the time, and moreover was on the other side of the ocean. note . However, it did give the Western Allies the loyalty of one of the greatest industrial and commercial powerhouse on the planet that was not already on their side, and a potentially vast military in which veteran Marine and Regular Army and Navy troops could be supplemented by huge numbers of conscripts, all of whom began being shipped across the Atlantic in droves during 1917 and 1918. The Central Powers recognized the problems with this and pulled out all the stops to try and knock the major Western Entente nations (by now the only continental Entente powers still in the game after the fall of Russia) out of the war while the US was still mobilizing, but their do-or-die attacks against Italy and the Western Front ultimately broke down, leaving a broken and demoralized German-led alliance that was outnumbered, outgunned, increasingly unpopular at home, and about to be squeezed from all sides, helped by the growing Allied skill at fighting submarine warfare. The result was that the Allies kept pushing for about 100 days and ultimately broke through on all fronts in summer 1918, with Austria-Hungary and Germany suing for peace in October-November 1918.

The submarine threat caused the Allied to adopt convoysnote  to protect their shipping and to seek out ways to detect and dispose of them, starting with depth charges and hydrophones and proceeding through sonar to radar and radio direction finding — as well as specific kinds ships to carry all of these things. Twenty years after the first World War Britain was still an island so the Germans tried the same naval strategy again — this time with significantly more success, since they'd also developed their "wolfpack" tactics in the interim. The idea behind the wolfpack was fairly simple—any submarine locating a convoy would report it to base, which would in turn vector all available U-Boats to the vicinity. The Allies in turn responded to heavy losses with new technologies — radar and aircraft, both land-based and flying from the small "escort carriers" mentioned above, fancier means of delivering depth charges like "hedgehog" and "mousetrap" and eventually even acoustic homing torpedoes. The Germans, in turn, responded with defensive homing torpedoes of their own, radar warning receivers, anti-sonar and radar coatings, the Schnorkel which allowed subs to cruise submerged while recharging their batteries, and ultimately the Type XXI, a very advanced type of sub that carried a larger number of torpedoes and was actually fast enough to run away from the subchasers, even while underwater.

Ultimately the end result of the battle of the Atlantic (which lasted from the beginning of the war in 1939 to the end in 1945, making it the longest battle in human history) was defeat for Germany. But that didn't mean it wasn't a near-run thing. And despite all the gee-whiz gadgetry the true key to victory proved to be the German's heavy dependence upon radio to control their Wolfpacks, which left the U-boats vulnerable to both high-tech code-breaking and low-tech radio direction finding. Meanwhile, on the other side of the world, the United States, despite having been drawn into two world wars largely over their objections to the unrestricted submarine warfare conducted by Germany, was ironically enough engaged in an unrestricted submarine campaign of their own against another island nation-state: Imperial Japan. This time with the technological balance firmly on their side the result was a resounding victory for the submarines. U.S. submarines sank thousands of Japanese ships, far more than all other arms combined, despite having spent the first 21 months of the war with defective (and often ineffective) torpedoes. Japanese submarines, in the meantime, were focused primarily on attacking warships rather than supply chains. Though they had periodic successes, this strategy was ineffective in the long run, and instead made the submarines vulnerable to attack themselves.

After the war, somebody came up with the idea that the newly-invented nuclear reactor would make a fine, nearly unlimited, energy source for a submarine, allowing the sub to stay underwater almost as long as its crew wanted to. And then, somebody got the idea — first proposed by, again, the Germans (they even had prototypes) — to arm them with rockets, this time nuke-tipped. And thus, thanks to wonders of nuclear physics, the sub was promoted from highly dangerous seaborne nuisance to strategic threat (H. G. Wells saw it coming). As a nearly unintentional side-benefit, nuclear power also made the noisy, clanky machinery of submarines much, much quieter, making true stealth under the water possible note . Non-nuclear submarines can also shut down any mechanical equipment, potentially rendering them entirely quiet at the cost of not being able to do anything.

Nuclear Power (1950s-present)

Underway on nuclear power.
Message from USS Nautilus (SSN 571), 17 January 1955

It was realised that nuclear power was not only useful for submarines, but other vessels too, which would not need to be refueled at sea. And fuel occupies space and weight that ship designers would often prefer to use for other things. Even burning fuel can cause problems if the empty tanks are not ballasted to maintain stability. Aircraft carriers especially benefit from nuclear power, since the tanks not used to carry fuel for the ship can instead be used to carry fuel for the aircraft. The United States proved the concept with USS Enterprise followed over a period of five decades by the ten-ship Nimitz-class.. Another class, the Gerald R. Ford-class note  continues to be built, the first ship having been commissioned in 2017. Nuclear-powered cruisers and destroyers followed, but nearly none remain in service (bar two of the Soviet/Russian "Kirovs"), mostly due to the end of the Cold War.

While there have been some safety concerns, especially early on and in the Soviet Navy (whose early nuclear shipbuilding program was very rushed), radiation has not proven to be the problem so much as cost. The major bar to nuclear powered ships is and always has been the expense. Nuclear ships are extremely expensive to build, their crews are expensive to train, and they are even expensive to decommission after you are done with them. Consequently, only a few countries were ever able to afford them, and even then a few. It's been calculated that the total cost of running a nuclear ship over its lifetime becomes lower than that of a conventional ship only for the fairly large ones: starting at about 12 to 15 kilotons of displacement, and few modern warships are that big. Basically only heavy cruisers and aircraft carriers can be justified to be made nuclear, and so they did.

However, building, equipping, and operating a modern full-sized fleet carrier—conventionally powered or nuclear—is so stupendously expensive that the U.S. is currently the only power willing to maintain even one of them. France, Soviet Union/Russia and now China also has a large carrier each, but these are a good 30% (Kuznetsov/Liaoning-class) or even 50% (Charles De Gaulle-class) smaller than a Nimitz-class, and also quite problematic at that. When things get that expensive it doesn't cost that much more to include nuclear power. And even then France, the only country other than than the U.S. to operate a nuclear carrier, had so many problems with her that they decided to make her replacement/complement a conventional ship. Also, given that the cost of maintaining even one fleet carrier is larger than many national defense budgets and anything less than a fleet carrier would be helpless against one (let alone eleven) it should come as no surprise that most countries other than the United States are investing in a different kind of naval air power: the guided missile.

Guided Missiles (1960s-present)

Our scientific power has outrun our spiritual power. We have guided missiles and misguided men.
Martin Luther King, Jr.

Coinciding with the development of nuclear power for warships, stand-off weaponry started to come into its element. The problem with weapons before this was that their effective range had always been limited by the ability to see the target, and hit him before he got the chance to evade. If you fire from too far away, even if your shot was lined up perfectly (not likely on a pitching sea), the enemy can still try to get out of the way before the projectile reaches him. Even the invention of radar and sonar didn't fully solve this problem, instead merely giving you a "higher" platform from which to look at the enemy from.

During World War II, a hard look was taken at the problem, and both sides came up with the same solution: find a way to let the projectile change its course in mid-flight (or swim, for torpedoes). You don't even really have to worry about your aim too much, if the weapon will follow the enemy around until it hits. Thus the guided missile was born. This carried implications beyond the obvious. Scoring hits not longer depended upon pumping as many shells as possible into the air. Increasing the probability that each weapon will hit means you don't have to fire as many of them, which means you don't have to carry as many of them. Self contained weapons need fewer men to service them, and self-propelled weapons don't produce any recoil. All of which meant increasingly powerful weapons could be mounted on smaller and smaller ships.

The Germans and the Americans had some success with with radio-guided bombs and missiles during World War II and both sides had also fielded successful acoustic homing torpedoes. The American air-launched Mark 24 "Fido" acoustic torpedo sank or damaged 27% of the submarines it was dropped on. The Germans even managed to sink an Italian battleship (after Italy switched sides and joined the Allies) using the "Fritz-X" air-to-surface missile. The Japanese managed to trump both the Germans and the Americans (and horrify the world) by damaging more than 300 ships using the human-guided missiles known as Kamikaze, sinking 47 ships and causing more than 15,000 casualties. But things really started to develop in the 1960s after the development of semiconductors resulted in massive improvements in electronic control systems.

Following the Japanese lead, the Soviets and Americans developed long-range guided anti-shipping cruise missiles, originally designed to fly high like normal aircraft and then dive on their target at very high speed — essentially pilotless kamikazes. Sea-skimmers followed later. At the same time, the dominance of air power also lead both sides to develop a myriad of anti-air missiles as well—and navies, now terrified of the damage anti-ship missiles could do to their ships, realized that since an anti-ship cruise missile is basically a small, unmanned, explosive aircraft, ships had now been given a way to defend themselves again. Both sorts of missile began to increase in range, power and accuracy.

This caused problems with guidance, namely the fact that most radars can't go too far beyond the horizon — the ones that can wouldn't fit on a ship, leading to developments in target data-sharing, allowing an airplane, helicopter or submarine to send course corrections to the missiles in flight. The Soviets did some work on radar satellites to detect U.S. carrier groups from space (the stupendous energy needs of which also meant that they also had the lead in the satellite-based nuclear reactors), the Americans worked on anti-satellite weapons, so the Soviets did the same.

Originally considered poor man's airpower for countries that couldn't build or afford carriers, missiles soon changed the face of naval warfare because they allowed a relatively small boat to pack a big punch. Like the submarine and airplane before them, missiles primarily appealed to a relatively weak naval power hoping to leapfrog a larger rival, in this case the Soviet Union. In the Six Day War of 1967, Soviet-built "Komar"-class missile boats in Egyptian service sank several Israeli vessels, including a destroyer, which was a wake-up call for everyone. Some were heedless though, and in the 1972 war the Indian Navy pretty much destroyed the Pakistani naval base in Karachi with two extremely successful raids using Soviet-built missile boats, sinking a number of Pakistani vessels and blowing up much of the port's land-based infrastructure while sustaining zero losses. These episodes proved without doubt that firepower had at last won the ancient struggle of gun vs armor.

In this new environment, the only real defense was not getting hit. Small, fast missile boats rapidly replaced larger vessels in the navies of smaller states because they were significantly cheaper to build, maintain, and man while their powerful missile batteries offered the same sort of David-vs-Goliath defense capabilities that torpedo boats had offered against battleships in the previous century. (They also have the advantage of being a lot more useful for most of the peacetime missions navies have, like fisheries patrol and search and rescue.) Countries with transoceanic commitments that required large ships couldn't take that route, however, and this inspired all sides to work on countermeasures like jammers, chaff, surface-to-air missiles that could shoot down anti-shipping missiles, culminating in the U.S. Aegis system, and on gatling gun based automated "close in weapons systems" for last ditch defense.

In 1982, two modern navies went to war over some islands in the South Atlantic. Argentina demonstrated the effectiveness of sea-skimming cruise missiles using the (in)famous French-made Exocet. The British demonstrated the effectiveness of chaff as a decoy. Both demonstrations were particularly vivid in the case of the Atlantic Conveyor on 25 May, where the chaff from one vessel attracted two Exocets but led to the missiles acquiring the next target they could, a requisitioned merchant vessel. Two missiles designed to destroy a warship made short work of the Atlantic Conveyor which promptly sank, resulting in the loss of twelve men and a lot of helicopters. It also meant the British troops had to walk across the Falklands to capture Port Stanley. There was a sense of the old here too — General Belgrano, an Argentine gun cruiser of World War II vintage (previously the USS Phoenix) was sunk using torpedoes of World War II design from a nuclear-powered submarine, an act that to this day constitutes the only confirmed kills by a nuclear powered sub in combat. Gotcha.

Naval warfare sped up tremendously here — in the case of HMS Sheffield, the time from Exocet launch to impact was four minutes — with Sheffield only getting five seconds warning as they disbelieved the alert until it was too late. In a confrontation between the U.S. and Iranian navies precipitated by the mining of USS Samuel B Roberts an Iranian patrol boat was sunk so quickly by two U.S. missiles that a third missile couldn't find enough left of it to hit. On the other hand, two Iraqi-launched Exocets failed to sink the frigate USS Stark due to a combination of sheer luck (HMS Sheffield lost her high-pressure fire extinguishing system due to the missile impact), stout construction, and outstanding damage control work on the part of the crew, proving that even in the missile age luck and seamanship still count for something.

In the 1991 Gulf War, anti-missile missiles finally proved their effectiveness when a British Sea Dart destroyed an Iraqi "Silkworm" missile fired against USS Missouri, one of the world's last battleships and ironically the one ship in the world least likely to be damaged by it.

The 21st Century

While there have been no major naval conflicts in the 21st century, some armchair-generals have speculated that the standard carrier group still in use by the U.S. has been rendered obsolete in that they are basically large sitting ducks to the newer technologies above. The theory goes that a multi-billion dollar carrier can apparently easily be overwhelmed by multiple low cost missiles approaching at Mach 2+ speeds from different directions. Actual non-armchair (lieutenant) general Paul K. Van Riper used a similar strategy to "sink" 16 American warships, including a carrier, during the 2002 Millennium Challenge wargame, though the feasibility of those results are questionable, at best.

Navies are not blind to this idea, as it's been considered as a possible scenario since the late 1970s: the infamous "Backfire" raid scenario, consisting of supersonic Soviet bombers firing numerous missiles, haunted U.S. planning throughout the late Cold War. The U.S. Aegis system installed on cruisers and destroyers was designed with the express purpose of defeating this threat, and is capable of engaging dozens of small, fast moving targets simultaneously at any range from "beyond visual" to "knife fight". In fairness, there has not been a major missile engagement since the system was invented, so it is unknown how well it would work in a real fight.

The new British Type 45 destroyers are another attempt at dealing with this problem. The official stats claim it has the smallest radar profile of any modern surface warship and an air-defence system capable of destroying multiple objects the size of cricket balls traveling at Mach 3. This argument also begs the question of who exactly is going to be firing all those anti-ship missiles; after the end of the USSR, the potential for a massive missile attack on a carrier group has gone way down. Russia, despite a recent naval buildup combining several new missile-heavy designs and a generally more aggressive attitude currently has neither the resources, the intention, or the warm water portsnote  to enter into another major naval arms race. So for now the states of the world seem content (or at least resigned) to the allow the U.S. Navy to continue to dominate the world's oceans just as they have since WWII, a situation that seems unlikely to change as long as the U.S. Navy outguns all of the world's other navies put together.

Ballistic missiles have also been proposed as a "carrier killer" weapon, most notably by the Chinese. They would have the advantage of nearly unlimited range, and allow for extremely fast attacks with minimal warning. However, there are questions about whether they've really created an accurate enough weapon to be effective without a nuclear warhead, and whether they would actually ever consider using one even in a declared war—all ballistic missiles look the same on radar, and in general countries don't want to fire any kind of ballistic missile towards an adversary out of fear it might be mistaken for a nuke, which could lead to said adversary responding with actual nukes.note  Additionally, several navies—most notably the US—have begun installing Anti-Ballistic Missile systems on their escort ships. The eternal battle between offensive and defensive weapons continues.

Other emerging naval technologies include:

  • Stealth Design: Making ships harder to detect by radar, sonar or infrared makes them harder to destroy and allows more opportunity for surprise attacks, but requires some clever engineering and exotic materials to be effective, and a change in surface ship tactics to take advantage of their newfound invisibility.
  • Railguns: These have the potential to bring back the age of the battleships, in a way. A railgun or similar electromagnetic weapon would have the ability to take a heavy slug of metal and accelerate it to ridiculous velocities (Mach 6+), to the point where it would have so much kinetic energy on impact with a target that a warhead is pointless. You could as easily bombard land targets hundreds of miles away as destroy ships and aircraft nearby with the same weapon. This is also fast enough that if the fire control system were sufficiently accurate it could be used as an anti-missile system. Eliminating explosive ammo also gets rid of a major shipboard fire hazard and allows the interior layout of ships to be re-arranged, as protected magazines are no longer required. Even simple economics favor railguns, as a 10lb steel spike and generating the electricity to fire it cost significantly less than a 1000lb anti-air missile, and you can fit many more spikes than missiles onboard. Drawbacks would however include the ridiculous power generation capabilities required to charge up the gun's capacitors, and the problem of somehow defending against a railgun hit, not to mention the problems current railgun prototypes are facing with keeping the rails from deforming during firing. The U.S. Navy has taken the lead in developing these and currently holds the world record for most powerful railgun shot, at 32 megaJoules muzzle energy. The real-world meaning of 32 megajoules? The muzzle velocity of the BAE railgun tested was 2520 m/s, well above seven times the speed of sound through air.
  • Lasers: Similar to the above, sufficiently powerful lasers would serve as an excellent line-of-sight anti-surface weapons and also be highly effective against aircraft. Additionally, a laser requires no ammo, though subject to vast power requirements. Also currently being pioneered by the US, which possesses an air-based one that can shoot down missiles, and a sea-based one that can light small boats on fire from miles away.
  • Unmanned Vehicles: Unmanned surface, flying, and submerged vehicles (USuV, UAV, and USV, respectively) all exist in the world's navies, though they are currently used only for specialty jobs seen as too dangerous for human-piloted vehicles, like mine clearance, target spotting and surveillance, and as target drones. However, several navies are trying to create combat vehicles with no crew-members. Once again, the U.S. does a lot of this. While expensive, the public sensitivity to casualties in war make them ideal for a country that has the naval budget to develop and build them. The ability to send an unmanned vehicle into a dangerous combat situation also has implications for the conduct of battles, as commanders who previously might not have risked people's lives for riskier strategies may no longer have such hesitation.

Submarine and antisubmarine warfare tactics continue to evolve but it is still not known exactly what a modern submarine battle would look like; as noted in the Hot Sub-on-Sub Action page, only one such engagement has ever taken place and it happened without nuclear subs and guided torpedoes. Germany has returned to the U-boat business, developing a new line of submarines which are much quieter that are powered by hydrogen fuel cells.

The U.S. has also recently become concerned about littoral warfare, especially boats packed with explosives in a crowded shipping channel, as demonstrated by the attack on USS Cole in 2000. Concerns over the DDG-1000 class' ability to operate there led to its cancellation after four examples. Another examples from 2010 is how an old North Korean submarine sunk a modern South Korean corvette in a sneak attack; it took an extensive forensic investigation to figure out what really had happened, and even then some doubts remain, though mostly raised by the DPRK traditional supporters.

Part of the difficulty of predicting what the next naval war will look like is trying to figure out who it would be fought between. A fight between major powers like the U.S. and rising power China might look like the massive, deep-water all out missile-and-torpedo-fest everyone was predicting would happen between late Cold War U.S. and USSR, complete with carrier battles, furballs with high-performance fighter aircraft, nuclear subs on both sides, and amphibious invasions. On the other hand, it might be between two smaller navies where the largest ship available is a frigate and most of the combat is done at visual range by patrol boats with machine guns. Some theorists think instead that the next waterborne conflict won't be fought between empires and nation-states but rather between non-state actors—terrorist groups, private military contractors, etc, or as a "waterborne insurgency" of a state vs. a non-state. Whichever conflict one choses influences the vision of future combat.

In many ways, the current naval scene is a lot like it was in the mid-to-late 1800s; no one is sure how the scene will resolve; everyone is trying various different weapons to see what works, but no one will really know until things get combat tested.

All this assuming no one simply puts ships in orbit for the ultimate in "high ground."