As the technology used to wage warfare has advanced, all new weapons and tactics have risen to use them. In the process, previous methods become far less prominent, and often eventually disappear altogether. Most modern navies have all but abandoned battleships, and the only blades today's soldiers carry are knives.
But in the future... what if technology takes a sudden and (un?)expected turn? The advent of military-grade lasers and fire-control systems that are decidedly not Point Defenseless makes missiles useless and taking aircraft into battle suicidal. All those modern aircraft carriers and missile cruisers suddenly become obsolete, and the battleship is king of the seas once more. What if personal-scale Deflector Shields make swords and spears viable weapons again?
This occurs a lot in Speculative Fiction, where some discovery or advance in science or technology has the net effect of rendering the last 20 to 200 years of military tactical development moot, forcing a return to the methods of an earlier time of warfare, often still with high-tech spins on the old gear. For example, if large close-combat weapons become viable again, they may develop Laser Blades, Hot Blades, or Vibroweapons. This overlaps with Retro Upgrade.
Often invoked by creators who wish to justify Hollywood Tactics or other kinds of martial Rule of Cool; the justifications may or may not be convincing, depending on how much thought went into them. See also Break Out the Museum Piece, when this happens in a more immediate sense. Compare Archaic Weapon for an Advanced Age, which does not require this trope, but will frequently overlap with it when it does occur.
- In Attack on Titan, the military is primarily trained in double swords and hand-to-hand combat because the unique biology of Titans makes projectile weapons nearly useless, though cannons still get used in Titan defense to slow them down and rifles are kept around to enforce the law and to deal with possible civil wars or uprisings.
- Averted as of the revelation of the Kingdom of Marley and the rest of the world, which hovers around the area of WWI, with bolt-action rifles, machine guns, and aircraft (both of the lighter and heavier-than-air variety) being commonplace. Tanks have yet to be seen, possibly due to Marley's using Titans as Cannon Fodder and Elite Mooks making their usefulness moot, but with the introduction anti-titan cannons, they could turn up, a point of serious concern to Marley since they could lose their place as the world's superpower if Titans were rendered obsolete, and a very serious concern to Eldians, since their titan-shifting abilities (voluntary or not) are the only reason Marley hasn't started a campaign of genocide against them.
- Mobile Suit Gundam introduced the Minovsky Particle, which when scattered across an area did a number on detection and guidance equipment, forcing both land and space combat back into visual ranges. It should be noted that the arming of the Zaku II with a Heat Hawk was something of a predictive move, with Zeonic designers figuring that the Federation would develop their own mobile suits sooner or later, and added the weapon just in case.
- Mobile Suit Gundam SEED has "Neutron Jammers", which prohibit fission reactions and jams radios. The result: no nukes, everything runs on batteries, and, you guessed it, close-range combat.
- In Nikolai Dante, small unit infantry tactics have regressed to the Napoleonic era by the 27th century. Soldiers regularly carry swords alongside firearms and duels are not uncommon. Lampshaded by Dmitri Romanov, who notes that previous generations (i.e. Our era) tried to civilised warfare to no avail and that war needs to be wholesale slaughter. Combined arms warfare does exist, but there's one occasion where Dmitri holds back air support so he can win in style. This ends up biting him in the ass.
- Played with in the Book of the New Sun. Most of Urth's technology has regressed, so most soldiers are armed with crossbows and slings, while others have lances. Crossbows and slings that have pyrotechnic ammunition, and lances that can fire bolts of energy. The cavalry charge is much in evidence, although horses are extinct and their replacements run faster than a motor vehicle.
- CoDominium: To keep the the status quo, the titular Soviet-American alliance has banned most research. While their Space Navy hasn't suffered (being needed to colonize and police the stars), the restrictions has caused a regression in ground combat. Improvements to computer countermeasures, railguns, and man-portable missiles have made aircraft obsolete. Improvements to body armor has limited effective sizes of ammunition. 21st Century warfare resembles early 20th century combat. In addition, the colonial worlds lack industry, so very few can build tanks or artillery. Unless it's a CD Marine outfit or a merc company from one of the richer planets, often battles on colonial worlds are infantry only.
- In Dorsai!, long range countermeasures have actually reduced the effectiveness of many weapons. Civilians have better, more advanced firepower than most soldiers. As a result, many troopers rely on simple, effective weapons.
- Dune has "Holtzman fields", which radically changes war. Artillery is obsoleted, most projectile weapons can't penetrate the field, and even lasguns can't be used due to "explosive pyrotechnics". As a result, ground combat is relegated to sword combat. The exception is found on the titular planet — shields attract Sand Worms, and as such can't be used for the most part, causing warfare on Arrakis (Dune) to shift back the other way. This spreads to the rest of the empire in God-Emperor of Dune when shield technology is banned.
- Hammer's Slammers: Thanks to accurate targeting and Powerguns, aircraft has practically disappeared from the field of battle. Artillery fire can be interdicted by powergun blasts, but shells still manage to get through. Nukes are rendered useless thanks to "nuclear suppression fields". In the backstory, tanks themselves almost disappeared from the battlefield due to developments in technology — man-portable anti-tank rockets, pin-point accurate missiles, and helicopters that could strike rapidly all made tanks rapidly obsolete until fusion and powerguns made them practical again.
"Technology had dragged the tank to the brink of abandonment. Not surprisingly, it was technology again which brought the panzers back."
- Impeller drive in the Honorverse places an impenetrable field right above and below starships, meaning that ships can only be hit in two dimensions or conversely fire from those same sides, thus broadsides in 3-d space.
- In the Legacy of the Aldenata, the invading Posleen have point-defense strong enough to neutralize our missiles and aircraft. Necessitating the revival of battleships on sea and "land ships" on land with a lot of armor and big guns.
- Lensman: Battleaxes make a comeback in boarding actions because personal shields have repulsive force proportional to the velocity of the incoming object, similar to Dune.
- In A Lord from Planet Earth, the ubiquitous use of neutralizing fields renders all forms of explosives and energy weapons useless, bringing back swordfighting as a primary form of combat (although more modern combat is still present, wherever there are no such fields), with a twist. The most commonly used weapons are Absurdly Sharp Blades called planar (or atomic) swords. The way they're used is also completely different from what one expects. There are no parries and Blade Locks, since one of the blades will always slice through the other. Instead, the skill is instead in evading and properly positioning your own blade, so that it's the opponent's blade that gets sliced. Timely sharpening is also key, as planar swords grow dull with each swipe, and each blade is limited to about 1500 "sharpenings" using the conveniently located button.
- On Starfist, the creation of the "Straight Arrow" Anti-Vehicle missile is so effective at destroying tank warfare that the only person to think of bringing it back in any major warfare capacity in the hundreds of years afterwards is the bad-guy warlord of the book Steel Gauntlet (and this forces the Marines to Break Out the Museum Piece themselves-namely, the knowledge on how to produce the missiles, as well as what few working models remain(ed)). Even then, warfare remains a business done purely by infantry, with (comparatively to modern day) very minor combined-arms (artillery, drone, orbital bombardment and APC) support.
- In World War Z, the world's armies have largely abandoned tanks, jet fighters, aircraft carriers, and indeed most modern tactics, as such equipment and tactics are poorly suited for fighting masses of unarmed, Nigh-Invulnerable zombies that can't feel pain or fear. While trucks and cargo planes are still invaluable for logistics, and armored infantry fighting vehicles like the Bradley are also useful for clearing out urban areas (where a massive horde of zombies can suddenly emerge from around a corner), assault rifles, grenades, and bayonets have been replaced — the new weapons of choice for most soldiers are semi-automatic rifles and the "Lobotomizer", a cross between a shovel and a battleaxe. The squad is also no longer the base unit for organization of soldiers — instead, they are organized into lines and fire in accurate, devastating salvos, like something off of a Napoleonic battlefield. More modern equipment is still kept in reserve for fighting rebels, separatists, survivalist holdouts, and enemy nations, but otherwise spends most of its time mothballed. Notably, Russia and China are among the few countries that stick with 'traditional' combat tactics and weapons in their fight against the zombies, and both countries suffer massive casualties as a result; the Russians held together solely due to religious fervor, while the Chinese almost fell apart entirely until the military brass launched a coup against the Communist Party leadership and turned things around.
- Doctor Who: "Genesis of the Daleks" shows Skaro, the home planet of the dread pepperpots, was undergoing this because of just how long the Forever War on that planet had been going on. Both sides had started out with nukes and chemical weapons, and by the time the Doctor and crew arrive, the soldiers are fighting with guns or even bayonets, because they're running low on bullets by that point. The Doctor speculates that if they go any further, both sides will be forced down to bows and arrows. We see this is true on revisiting this war in "The Magician's Apprentice".
- The Expanse: The lack of Subspace Ansibles in this series makes it so that most space-faring navies must depend primarily on the actions of individual captains and "on-site" admirals rather than the command centers of Earth and Mars, in effect loosely mimicking the age of naval warfare from before the dawn of mass communication and radio technology.
- In BattleTech, warfare is dominated by Battlemechs and lasers are commonly used weapons. However the first two Succession Wars have knocked back most Inner Sphere's technological progress resulting in most fights limited to close range combat. The Clans however possess more advanced technology than the Inner Sphere but they intentionally made most of their fighting limited to honor duels, to hone their skills and limit their losses. One response to the appearance of the Clans in the Inner Sphere was for the latter to produce 'Mechs armed with melee weapons (Axes, Clubs and Swords). This being the extreme end of the idea of nullifying the range advantage of Clan weapons by fighting at close range.
- Mortars use to be standard weapons, but were rendered obsolete by LRMs that have superior range. Centuries later when anti-missile systems are becoming more common, mortars are reintroduced as means to counter them.
- Later, the ravages of events like the Word of Blake Jihad caused precipitous drops in the availability of even basic war materials such as laser lenses, autocannon feed systems, and missile homing trackers. This led to a further devolution of technology in some places (particularly the rough and tumble Periphery) into what was known as Primitive or Retrotech, incorporating technically outdated equipment such as unguided rocket pods, slower-loading rifled cannons, internal combustion engine 'Mechs, and other less-advanced technologies. This tech has the benefit of being very cheap and easy to maintain/replace, even if it isn't particularly good.
- The old Manhunter universe had swordsmen who specialized in fighting aboard spacecraft, where guns are impractical because of the tendency of stray bullets to punch holes in the hull and/or destroy necessary equipment.
- Mutant Chronicles: When the Dark Symmetry (a cosmic horror force) is released, advanced computers become evil and electronics become unreliable. As a result, warfare (and pretty much everything else) regresses to The '70s.
- In Warhammer 40,000:
- Though modern weaponry has not been replaced (and in the case of the M2 Browning, still survives as the "heavy stubber"), melee combat is back again as regular fare on battlefields, and nearly every army in the setting has dedicated assault units with a Sword and Gun loadout. When you're a hulking half-fungal monstrosity, psychic bullet-dodging alien, hyper-evolved killing machine, or a daemon from Hell, close combat isn't that stupid an idea, and when you're a bunch of Puny Earthlings facing those aforementioned threats, some CQC training might help the men survive a few more seconds if the enemy reaches your gun line.
- Some Imperial Guard regiments, especially conscript or penal ones, still fight in massed formations even though explosives and automatic weapons are abundant in the settings. However, since Lasguns aren't powerful enough to kill most enemies in one shot, having men in massed formations firing in volleys can rack up more kills than letting them disperse and shoot individually. It helps that the Imperium has more people than they know what to do with, so having hundreds of low-skilled men die for any enemy killed is a perfectly viable tactic.
- Warhammer Fantasy: The Bretonnians still have a medieval conception of warfare (aristocrats on horses, peasant levies on foot), despite being next door to the late-Renaissance Empire who use muskets and cannon. The main reason this is in any way viable is literal divine protection that allows said aristocrats to charge musket lines and emerge victorious.
- Ace Combat Zero: The Belkan War is rife with references to Arthurian legends and medieval warfare, so its inevitable that the warfare reflects this as well.
- To start, the setting is centered around a country on the verge of economic and industrial collapse attempting to retake former provinces that have since formed their own independent countries. The former provinces, of course, don't want to go back to being provinces, but they also barely have a standing military to call their own, and so they rely on mercenaries to fight for them, resulting in a sort of throwback to smaller countries paying sellswords to defend their lands from more powerful countries.
- One of the most iconic regions of the war is known as "The Round Table," a massive resource-rich but isolated area where natural electromagnetic radiation tends to restrict the use of ground forces, and so the only way to "control" the Round Table is to control it from the air. As a result, aerial skirmishes in this area are massive, with multiple squadrons duking it out in legendary furballs where only the strongest and most skilled survive, akin to the actual chaos of a medieval battlefield.
- And finally you have the final mission, where you must engage a prototype fighter plane with EM shielding that prevents missiles from locking on and hitting. The only vulnerable spot on the plane is the two intakes, meaning you have to approach it from head-on, while he does the same. The result is jousting. In midair. At Mach 3. With fighter jets.
- In Armored Core, the advent of powerful mecha - particularly the NEXTs in the 4/For Answer continuity, have rendered close combat using Laser Blades an extremely effective strategy, since such mecha are both very fast and extremely resistant to gunfire. Thus, a Sword Fight between thirty-foot-high mecha moving at more than the speed of sound is not an uncommon sight on future battlefields, as a single strike from some of the more powerful Laser Blades can be a One-Hit Kill.
- Autonomous air defense systems have rendered things like drones and ICBMs useless in the future of Call of Duty: Black Ops III. As such the demand for capable foot soldiers is once again on the rise and cybernetic augmentation is there to make them all the more effective, albeit at a possible price.
- Command & Conquer: Red Alert 3: Due to Time Travel being an integral part of the series, warfare doesn't so much regress as get reset, but taking familiar paths every time.
- Best seen with the Imperial faction, which uses units inspired by its real-life WW2 counterparts with much higher tech (i.e. kamikaze drones, superheated katanas, Ninja that can take out Power Armor, etc.).
- The 3 naval heavy units have equivalent ranges and damage, despite one being a missile cruiser, one essentially the Yamato firing lasers instead of shells (and can ram enemy ships to sink them), and one an aircraft carrier (admittedly a scaled-down one that launches drones).
- This trope pops up over the course of the Command & Conquer Tiberian games.
- In Tiberian Sun, the Global Defense Initiative upgraded its arsenal with Walking Tanks and hovering weapon platforms, but by Tiberium Wars GDI reverted to just as advanced, but more conventional, units. The anti-grav units could be disabled by an Ion Storm, and the mechs were just too high-maintenance - plus, Tiberium Wars introduced a mechanic where a faction's Commando unit can run up and slap an explosive charge onto a mech's leg joint for a One-Hit Kill. So only one GDI subfaction in the Kane's Wrath expansion uses such units with great frequency, and all but the walking artillery pieces were mothballed by GDI at large.
- And on the Brotherhood of Nod's side, Earth's deteriorating enviroment forced them to abandon the subterranean units they used in Tiberian Sun. However, by the events of Commander And Conquer Tiberian Twilight, thanks to GDI and Nod finally getting the Tiberium situation under control, both sides have regained their unique technology, with GDI's combat walkers and Nod's subterranean technology back in action.
- Devil's Third is premised on the "Kessler Syndrome" theory: that is when man-made satellites in Earth orbit collide, the debris will begin a chain reaction that will destroy other satellites in sequence. In their world this has indeed happened, which forced the end of technologies such as GPS and satellite imagery and wars are fought without these advantages.
- Averted in the Dune II and Emperor: Battle for Dune games. Unlike the books (shield technology makes many projectile weapons obsolete), the various factions operate tanks, artillery, and machine guns just fine. Dune II has benefit of being set on Arrakis, where Shields are avoided to prevent the major local wildlife from going berserk. But in Emperor, all units are still usable even not on Dune, and House Ordos still uses some shielded units on Arrakis.
- In Mass Effect, the first game in the franchise featured advanced firearms with Bottomless Magazines that were restrained by an overheating system. This unbalanced the game too much in the player's favor so subsequent games replaced overheating with heat sinks, single use cartridges that absorb weapon heat and need to be replaced after a certain number of bullets are fired. The in-universe reason for this was that the galaxy's militaries collectively changed their weaponry designs after concluding that warfare was starting to focus around skirmishes rather than attrition and heat sinks allowed soldiers to fire continuously as long as they didn't run out of spares. Many fans complained that this was functionally no different than going back to using regular ammo, something that was poked fun at in the third game.
- In Metal Gear Rising: Revengeance CNT armour makes cyborg infantry nearly Immune to Bullets, so melee Vibroweapons have come back into fashion.
- EarthSiege and StarSiege have HERCULANs that don't show up in the Tribes series because they were difficult to maintain and less maneuverable than teams of power-armored soldiers with built-in jetpacks. Plus, technology had advanced to the point that less complex vehicles, like aircraft and tanks, could be assembled in just a few seconds with a special vehicle pad/assembler. Another benefit is being able to leave behind cheaply made vehicles when they get too damaged, instead of hauling back an expensive HERC for repairs.
- In the Big Head Press comic Phoebus Krumm, "S-fields" enable FTL travel but disable all electronics within the field, making space warfare essentially age of sail naval combat.
- Plush and Blood: Emperor Brown intentionally brought the majority of his advanced forces and supersoldiers to a heavily-contested nuclear reactor to judge himself - he wanted to see if his archnemesis Phoenix would be willing to doom the world with global nuclear fallout if it meant stopping Brown once and for all, with Brown's evil plan being Brainwashing for the Greater Good to create a world where nobody could act on hate. Unfortunately, Phoenix's lacky was all too willing to push the button out of spite. Ten years later, the entire world is a wretched wasteland where agricultural supplies are a myth, bandits use semi-auto revolvers, and the local caravans are all wagons and mutant slaves.
- In the future of S.S.D.D. advances in anti-air defense had made air and missile strikes nearly impossible, and fullerene armor made ordinary guns obsolete. Which meant most battles were fought on the ground, by men in suits armor hitting one another with hammers. "Oh, how far we have come." One of the major story arcs involves a war that ends when one side uses a Kill Sat to knock out their opponent's AA and launching a bunch of museum piece ICBMs.
- The aircraft carrier example given in the description is speculated by some military theorists to be on its way to becoming Truth in Television sometime in the 21st century, due to the increasing efficacy of anti-ship missiles. Given that these same missiles can also sink other large boats, the consequence of this would be that the future of naval warfare in this environment would resemble a mix of the mid-late 19th century (before the dreadnought race), with every surface vessel larger than a destroyer (the smallest warship that can operate independently in the open ocean) rendered obsolete, and the early 20th century, specifically the submarine warfare employed by Germany in the two World Wars, albeit with the proliferation of much more powerful and long-ranged weaponry. Such predictions take on an especially ominous tone for the United States, whose unmatched navy is built largely around the power of its carrier task forces; the other boats in the fleet are all there to protect the carriers. The biggest criticism revolves around sticking to the doctrine of building enormous supercarriers, whose fighter planes don't have the range to compete with the modern Russian and Chinese anti-ship missiles. One naval officer proposed to scrap the newest multi-billion dollar carrier programs and replace them with smaller, cheaper carriers, and put more money into developing more effective long-range fighter/bombers to counter the Russian and Chinese advantage.
- (Attributed to, but probably not) Albert Einstein:
"I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones."
- World War I featured many examples of previously-considered-outdated modes of combat being more effective than then-modern technologies and tactics.
- It was often said that the closest land-based comparison for aerial dogfighting was the combat of the Middle Ages, particularly the tales of knights dueling one another on even terms. This was seen as a positive thing, with many viewing aerial combat as the last bastion of martial chivalry in comparison to the horrors of industrial trench warfare on the ground (leaving aside the fact that pilots in World War I had arguably higher casualty rates, especially once air combat started picking up in 1917), and Ace Pilots for both the Allied and Central Powers would later be romanticized in terms similar to those of medieval knights.
- A few pieces of soldiers' equipment that had come to be considered outdated in the 19th century made a comeback during World War I. Grenades were considered obsolete with improvements to firearms easily stopping anyone trying to get close enough to throw them (the twists of trenches remedied that), and armor and helmets were considered expensive, overly cumbersome wastes of effort (the former was restricted to mostly entirely-still sentries, but the latter turned out to be a vital last resort for a man ducked in cover getting raked by shrapnel). Said equipment has improved and remained in use to this day.
- Military commanders originally idealized the rifle and bayonet, believing that waves upon waves of soldiers armed with this combination would go charging towards the enemy, firing well-aimed shots before switching to melee combat when they got close. This rarely happened. Even when soldiers survived long enough to reach enemy trenches, rifles with fixed bayonets were much too long to be effectively used in those tight quarters. Instead, soldiers turned to much cruder weapons, using large knives, short swords, clubs (often made deadlier with nails or barbed wire), and even brass knuckles when it came time to fight hand-to-hand.
- During the English Civil War, there were calls, especially on the Royalist side, to go back from muskets to longbows, on the grounds that that it was difficult for gunpowder production to keep up with consumption, and muskets aren't that much more lethal. Benjamin Franklin made a similar recommendation over a hundred years later during The American Revolution. In the end, though, muskets had one massive advantage over longbows: while it takes years to train a man to use a longbow, it only takes weeks to train that same man to use a musket with comparable lethality.
- The ancient Greeks used the phalanx (a mass of troops with very long spears) as the main part of their army. This strategy didn't last against the weapons and tactics of the Roman Legions. Fast forward a few centuries, and medieval armies made extensive use of pikemen (a mass of troops with very long spears), as they were the best way to prevent knights from overrunning your lines.
- In The '60s, a view emerged in the US military that the rise of guided missiles had rendered dogfighting obsolete, and so new fighter jets like the F-4 Phantom II did not have machine guns or cannons built in. Air combat in The Vietnam War, in which North Vietnamese pilots shredded their American counterparts in close-range dogfights where their long-range missiles were ineffective, demonstrated the hard way that this was not the case. Machine guns, cannons, and the training to use them returned to the fore very quickly.
- In the early 2000s, the US Army switched to the Army Combat Uniform, which featured zippered fronts and velcro pockets. However, actual use showed that the zippers and velcro quickly became clogged and were noisy to use, resulting in later version switching back to buttoned enclosures. The Universal Camouflage Pattern, meanwhile, looked futuristic but turned out not be very effective (unless used against ugly couches◊). Because of this, the US Army soon switched to the Operational Camouflage Pattern which looks like a faded version of the woodland pattern used throughout the 80s and 90s.