"Oh, this old thing? She's nothing really. You should see the real heat I'm packing back home."note President T. Roosevelt depicted as defending the United States' commercial interests in Latin America from the European powers.
The demonstration or display of military force in a threatening manner to encourage a country's 'co-operation', done without issuing blatant threats or actually engaging in military action.
For example, sending a fleet to fight a practice battle just off the coast of a country that's not giving you what you want is a classic example of gunboat diplomacy. The idea is to remind the target that you're stronger than they are, so if they don't do what you want you can always destroy their stuff and kill their people.
If the power playing the Gunboat Diplomacy trope is (a great deal) stronger than their opponent, this trope is win-win for them - if the target destroys the military force you used to threaten them, then you're perfectly justified in doing whatever you like to them short of genocide. Even if they don't actually attack you, you can always make it look like they tried.
Still pretty common today, even though the Cold War is over — chiefly involving the USA's dozen Aircraft-Carrier battle fleets, or tens of thousands of Russian Soldiers.
Compare with: Appeal to Force and Aggressive Negotiations. Overlaps considerably with Flaunting Your Fleets because this trope is largely about trade disputes (even today, 90% of the bulk/weight of all modern trade is by water-based transport), which leads to the occasional Naval Blockade.
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The Sand Pebbles depicts Western gunboat diplomacy in 1920s China. Quite literally: the setting is a gunboat.
The Howard Taylor novel Show of Force starts off as this by both sides over a missile deployment in the Indian Ocean and ends up turning into a full-scale naval battle.
In The Bear And The Dragon, attack subs are maneuvering near the Chinese coast long before hostilities begin, along with naval ships anchored in Taiwan, and Executive Orders has a premier tank squadron training in the Negev desert just before the UIR's invasion of its neighbors. Debt Of Honor subverts the whole thing by having the US and Japan conducting a joint training mission, and then having the Japanese navy doing the equivalent of cold-cocking the American forces returning to Pearl Harbor.
Considered, but not actually implemented in Rainbow Six, where the Rainbow troops were considering making their existence public just intimidate the to terrorists into keeping their heads down.
The Empire liked this. There's something called the "Tarkin Doctrine", which basically goes that it's better to rule by fear of force than force itself.
Threatened to happen in Starfighters of Adumar. Both the Empire and the New Republic were trying to win over a neutral world, and both had beforehand signed treaties stating that if they were not the favored party, they would withdraw all forces for three days and not return except under "formal banners of truce or war". The Empire intended to ignore that if it came to it, but the Imperial in charge hated being ordered to break his word so much that the New Republic ambassador, Wedge Antilles, was able to talk him out of it.
The final book in Harry Turtledove's Worldwar series features two spaceships. The first is Admiral Peary which is close to the conventional ships The Race uses and comes to negotiate on fair terms. The second is the Commodore Perry. Its purpose is not to negotiate on fair terms...
The Admiral Peary is armed with nukes, as a safeguard against the lizards doing anything bad to Earth in their absense. If that isn't gunboat diplomacy, I don't know what is. The Commodore Perry is an FTL-capable ship that took only 5 weeks to get to Tau Ceti. The mere fact that is was able to do that freaked out the Race more than the weapons it carried. Even if they managed to destroy the ship, the humans would just send another that could attack as soon as it arrived in orbit in a matter of weeks, as opposed to decades.
In the Vorkosigan Saga, Aral Vorkosigan pulls a clever reversal of this; he draws up a list of a neighbouring polity's top five requested diplomatic concessions and suggests it as an agenda for a summit. The diplomacy, in this case, is purely so that he can get his gunboat closer to where he suspects the action will take place. He's right, and it results in one hell of a Gunship Rescue moment.
Pierre Le Sanguinerre was the warleader for Emperor Dorca who carried out such things on recalcitrant vor.
In Star Trek: Articles of the Federation, United Federation of Planets President Bacco resorts to this when overseeing negotiations between the Carreon and the Deltans. The Deltans require a new water reclamation system for their planet, and the Carreon have the design they need. Because of an old feud, however, the Carreon refuse to negotiate properly. Bacco ends up using the implied threat of Federation military strength to stop the Carreon messing the Deltans around. As she tells the Carreon Ambassador, diplomacy is the means by which conflict is avoided. If Carrea won't negotiate in good faith, the only remaining option is war- and she makes it clear Carrea wouldn't stand a chance.
The novel The Romulan Way includes this in the second attempt at contacting the Rihannsu (Romulans), as the Federation had sent the starship Balboa with the Stone Mountain in the general area ready to help. The Rihannsu, paranoid due previous experiences with aliens that faked pacific intentions before attacking, annihilated Balboa with fifty of the seven thousands small warships they had built in the three years since the first attempt at contact, and then captured Stone Mountain and started making rude copies of its warp drive and advanced weapons to fight the Earth-Romulan War.
The sequel Swordhunt had the Rihannsu asking to renegotiate the Neutral Zone with the negotiations to happen of a neutral ship provided by the nomadic Lalairu, and all parties engaged in this: the Federation shows up with a squadron of warships composed by four Constitution refit-class heavy cruisers including Enterprise (commanded by their old nemesis Kirk) and two of the new Constellation-class long range cruisers, and commanded by one of the best and most aggressive commodores in Starfleet; the Rihannsu showed up with four heavy cruisers of a new class and two heavy cruisers of a bigger new class; the Lalairu sent the Mascrar, a colony ship that outgunned either task force.
The War of the Worlds is usually read as an allegory for the British Empire's gunboat diplomacy in the late nineteenth century.
This is standard policy for the Earth Federation when dealing with space-faring aliens in Mikhail Akhmanov's Trevelyan's Mission series. This is justified, as humanity's first (and many subsequent) encounters with aliens haven't exactly been on friendly terms. As such, all ambassadors are ferried by top-of-the-line cruisers. Then again, given that this 'verse has instant Casual Interstellar Travel, it's not that big a deal. The only time they did not do that is when a race of Technical Pacifists (who can somehow accurately predict possible futures using an advanced form of intuition) requested that no warships be present at negotiations.
In Jingo Vetinari shoots down the suggestion that Ankh-Morpork sent a warship to Klatch for this purpose on the grounds that, firstly, that sort of thing is not done in modern diplomacy and, secondly, Ankh-Morpork doesn't have any warships.
In just the second episode of Yes, Minister Hacker finds himself faced with a tricky situation involving the new dictator of an African state who, for various reasons, they need something from, but who is threatening to cause an embarrassing incident. The foreign secretary muses jokingly that in the old days they would just send in a gunboat. Hacker then asks if that is, absolutely, out of the question, to shocked stares.note The problem is solved when the Brits realize that the dictator is actually one of Hacker's old friends from uni, who has changed his name and converted to Islam as a political move; they settle the whole thing over a nice cup of tea.
In Yes, Prime Minister, Hacker (now PM), arranges for a full battalion of paratroopers to pay a goodwill visit to a small third-world country that may just be about to suffer from a Communist uprising, against Sir Humphrey's wishes.
Hacker: And the Americans say they have an entire airborne division standing by in case we need reinforcements. Sir Humphrey: Reinforcements of what, Prime Minister? Hacker: Reinforcements of goodwill, Humphrey!
Happens quite often in the various versions of Star Trek. Captain Kirk does it well because he is such a Badass.
Federation Diplomacy seems to consist of sending two diplomats to discuss things in a patronising manner, then holding the talks on a massively over-armed starship in orbit above one of the party's homeworld.
This is Lampshaded in the original script for Star Trek VI: The Undiscovered Country. Scotty protests "I haven't served 30 years in the engine room of a Starship to be accused of gunboat diplomacy!" One of the reasons why it happens so often is that the first contact goes violent often enough that you have to back it up with firepower simply to be safe — and as warp travel is generally too slow to get reinforcements there in reasonable time, that means the ships making first contact has to have that firepower. End result: the Federation keeps making initial agreements with newly discovered species while a starship capable of wiping out a civilization hangs around nearby.
A more explicit statement of the concept, also by Scotty: "The best diplomat I know is a fully-activated phaser bank!"
Which is completely logical. Carrot AND stick. Makes it clear that while the Federation is eager to be friends and to share their goodies with you, if you want to become their enemy instead, they have more than enough firepower to knock you down a peg or two. Diplomacy means nothing without the strength to back it up.
In The Sopranos, a real estate agent refuses to do business with Tony, so he has some of his men park a boat next to the agents beach house and play loud music.
Done by Delenn in Babylon 5, Severed Dreams. Widely considered a CMOA.
Earlier in the season, happens all over the place in A Voice In The Wilderness, with over a half-dozen races (including Earth and a previously-unknown race) all pulling this at once when it is discovered that there is some very powerful, very advanced technology buried beneath the planet that the station orbits. After a brief, inconclusive battle, the planet itself, now acting through its new caretaker, Draal, informs all involved parties that none of them can have exclusive control of the planet, and that any who approach without permission will be destroyed. The ship belonging to the previously-unknown race ignores the warning and promptly gets ventilated.
And subverted in Rumors, Bargains, and Lies, when Sheridan orders the Rangers to attack and destroy some random asteroids. The League races know that the White Stars have far superior sensors to anything they have, and thus assume that they were fighting an invisible enemy. Sheridan does nothing to convince them otherwise, and welcomes them into a new military alliance.
A common accusation is the invitation for Earth to join the Interstellar Alliance happened during the end of the rebellion, and included dozens of advance warships doing a flyover of the capital.
Andromeda: The whole reason why the High Guard had such fancy and overly powerful warships designed by now extinctVedrans was so the High Guard could flaunt their unimaginable destructive potential and deter beligerant species from hostilities during negotiations. Usually these were discussions that involved joining the Commonwealth either by free will or with the guns of a mile long warship that looks like an Italian-sportscar-in-space trained on them. The XMC class or Glorious Heritage-class heavy cruisers like the Andromeda Ascendant were built for exactly this purpose. They were the diplomatic flagships of the Commonwealth that usually operated without a task force for extended periods of time. The stupid amounts of firepower and the ability to crack an M-class planet like an egg in only a few minutes and a legion of lancers gave the High Guard captain a pretty good bargaining position. XMC heavy cruisers were also used for long range exploration because of this capability.
Of particular note is that in the post-Commonwealth dark age Captain Dylan Hunt frequently has to resort to gunboat diplomacy when dealing with the various planetary factions or powers he ends up dealing with.
Dylan: "Andromeda, how long do you think it would take you to depopulate this world?"
Also happens when Dylan is backing Prince Erik for the throne of Ne'Holland against the corrupt barons:
Erik: Our entire defense fleet?
Dylan: Rommie, how long would it take for you to destroy that fleet?
Rommie: 6.2 seconds.
Dylan: That long?
This didn't do much good against the Pyrians, whose ships were at least a match for the Glorious Heritage class. Also, unlike the Commonwealth, the Pyrians never went anywhere.
Battletech: When the second Star League was dissolved, the Word of Blake sent warships to the Lyran Alliance and Federated Suns capital planets to force them back into the Star League. Their leaders refused and the blakists open fired on their cities and launch a full scale invasion on their territories, this is the start of the Jihad which would spread to the rest of the Inner Sphere.
"Please Hello" from Stephen Sondheim's Pacific Overtures has America, British, Dutch, Russian and French admirals bringing Japan their demands for treaty ports and such, demands which are punctuated by cannon shots.
You can play a variant of this in Shin Megami Tensei II if your main character is sufficiently high level, when trying to bind demons. When the demon demands payment for joining you, simply refuse. It starts kicking up a fuss. You can then either calm it down, or rebuke it... which will scare it enough to immediately stop fussing and join you, for fear of what you might do otherwise.
In Mass Effect, it's said that the Alliance invokes this tactic as a deterrent to prevent pirate or slave raids on their planetary colonies. Want to attack? Go ahead! Just as long as you're aware of the whole fleet of heavily armed warships that's currently sitting no more than one Relay jump away.
During the First Contact War, it's implied this was part of the reason why the Citadel Council quickly stepped in and called for a ceasefire, recognising that the newly discovered Humans were proving easily capable of holding off the Turian military and the Council didn't want to run the risk of a Galactic War if there might be more of them!
This is more or less the underlying purpose of the floating city of Columbia in BioShock Infinite. Having a floating city appear in the skies over your country in an era when horses were still the preferred method of transporation and electricity was only just appearing in the most modern cities carried a lot of implied threat with it.
A common and legitimate strategy in Civilization. If you have a sufficiently large military force, you can declare war, invade your enemies lands, and take their cities... or open diplomacy with a neighbor and demand tribute from them, easy and pain-free. They may accept or refuse, depending on how powerful you are compared to them, whether you've made other demands recently, or whether or not you're simply asking too much. In Civ V, this is further expanded on with minor civs called City-States, from whom you can explicitly demand tribute in the form of gold or Worker units if you have a strong enough military near them. Doing so will anger the City-State and may also annoy major civs who are trying to curry favor with the City-State for the benefits it offers. There's even a late-game bonus called "Gunboat Diplomacy" which rapidly increases your influence with any city state you have the ability to demand tribute from.
At the height of its power in the 1800s, the British Empire became famous for this. It was said that the empire could quieten the whole of China by simply dispatching a single warshipnote Untrue, as the French found out in their 1884-85 Sino-French (mini-)War. France tried to take on China alone, and despite sinking half the antiquated Qing fleet was effectively fought to a standstill by modernised Qing Empire ground forces. The war reminded all the interested parties - France, Britain, Russia, Japan - that they needed each other's cooperation if they wanted to extract any more 'special concessions' (trade outposts, military bases) from The Empire Of The Qing - which despite supposedly being on its last legs, was regarded with renewed caution (until the much larger Sino-Japanese War of 1895, which revealed that the Qing's refusal to adopt a modern logistics/command system complete hamstrung their forces despite their size and usage of uber-modern weaponry).Boastful hyperbole, to be sure, but hyperbole with a point. It was taken to ridiculous levels with the Don Pacifico affair, when Britain's reaction to a British citizen in Greece being mugged was to send the Royal Navy over to blockade the entire country until the Greeks caught the man responsible and paid Don Pacifico compensation (although it should be noted that Pacifico was Jewish, and he was only the latest in a long line of British Jews to be abused in Greece, so the British did have, if you squint, a slightly nobler motive).
During the Second Opium War, the British and French sent what amounted to little more than three divisions (not even 60 000 troops)to escort their ambassadors to Peking - ostensibly in the hope that they would be recognised as equals rather than being made to do the kowtow and be officially recognised as vassals/servants. The Qing court umm-ed and ah-ed and eventually met them with armed force when they kept marching on the capital. However, their decently-armed but disorganised and ill-led force of 200,000 (which had zero experience of modern warfare to boot) was quickly routed and the Imperial Court fled the city still refusing to negotiate. The Allies stuck around and pillaged the place until they did.
Cleverly exploiting this was the way Russia peacefully and amicably acquired her Maritime Provinces in 1860. By negotiating a settlement and treaty to stop Allied troops from ransacking Beijing further, the Russian Embassador established a certain rapport with the Emperor was able to convince him that the sparsely-inhabited (Han Chinese were prohibited to settle there by the Manchu Qing dynasty, whose semi-nomadic people were the only people living there) lands in question were not only economically useless but also impossible to protect. He actually had a point there, as just seven years later Russia sold her lands in North America (the USA's current state of 'Alaska') to the USA for the exact same reasons. From that point onward, Russian diplomats were always keen to point out that Russia's acuisitions of Qing territory had been by mutual agreement and not made under duress - criticising at great length the French and the Japanese for their own less subtle approaches.
The governor of Guangzhou tried this against The British East India Company, without appreciating the close ties between The Company and the British government or the extent to which two hundred years of nothing more than border-skirmishes with steppe tribes and mountain-kingdoms had left Qing Chinese forces woefully inexperienced and ill-equipped for waging a full-scale modern war of the kind Europe had been fighting for four hundred years very nearly non-stop by that point (chiefly the Hundred Years' War, Eighty Years' War, Thirty Years' War, Seven Years' War, War of American Independence, War of the Spanish Succession, War of the Austrian Succession, French Revolutionary and Napoleonic Wars).
The 1807 Bombardment of Copenhagen was the culmination of several escalating pieces of gunboat diplomacy involving Britain and France: Napoleon wanted to invade England. To do so, he needed a navy. The Spanish Navy had been all but destroyed at Trafalgar, and thanks to purges, battle, bad luck, and blockade, the French Navy was spent as an effective fighting force. So he needed to either steal one or convince another power to become his ally. Sweden was too northerly and too pro-Britain, Russia was too big and too scary, and Turkey was too big and too far away. That left Denmark, with her almost indefensible land borders, small army, and tiny interior. Napoleon began by moving his army to the Danish border and demanding the Danish fleet. The British responded by sending a fleet to the Skaggerak and offering the Danes a bribe - one hand gives, the other takes. N The Danes politely refused the bribe but send their army to Holstein in the south of Denmark in order to reassure the British that they could stop the French taking their fleet. The British were not reassured. They landed on Zealand, surrounded Copenhagen, and demanded the fleet be handed over or the city would be destroyed. The Danes assumed no power would be so brutal as to destroy their capital. They had sadly overestimated the British. Copenhagen was bombarded by rockets, mortars, and warships for three nights, and the Danes, cowed, handed over their Navy to Britain without a fight. The bombardment was itself an act of gunboat diplomacy for all Europe: Britain made an example of a neutral and weak power in order to show Europe it's resolve to continue prosecuting the war against France, even as other powers vacillated. Copenhagen burned, in essence, pour encourager les autres.
The USA's Central-South American Banana Republics were, as per the page image, kept in line by constant reminders of the threat of force and the occasional USA-organised/supported coup d'etat. From a little after the US Civil War up until relatively recently - the Panama Canal incident being the latest example - this trope has been in force to some extent.
The page image also refers to a policy of gunboat diplomacy by proxy. The United States didn't want European warships intruding into the American sphere of influence; instead, the Europeans would ask the US to send a gunboat to apply pressure on their behalf.
Specifically, the page image is referring to the Monroe Doctrine - that the USA would resist all European attempts to interfere in 'their' zone of influence, i.e. the whole of the Americas. No-one took it seriously at the time, as the US was a third-rate power and it was clear that places like British Canada and Spanish Cuba were not part of the Americas, by this definition. Nor were places like Argentina, which was Britain's model Banana Republic. Anyhow, note how Roosevelt is aiming the gun at the monarchical European figure while the poor, defenseless Latin American cowers beneath him. The image doesn't actually show gunboat diplomacy as such but instead presents a benign ideal of it, as one would expect of a (biased) US political cartoon.
The SMS Panther is the Trope Namer and Trope Codifier, when it was dispatched by the German Empire to Morocco in 1911, during the Agadir Crisis. This incident popularised the phrase "gunboat diplomacy" and also contributed to the First World War.
The "Panther's Leap" also counts as a subversion of sorts, since the entire affair was a complete farce. She was ostensibly dispatched to Agadir to protect German citizens in the port, but this plan had one glaring flaw: there were no German citizens in Agadir. Realising this, the German government sent a telegram to the only German citizen in the area - a perfectly happy, unendangered man called Wilburg - and ordered him to travel 75 miles south to Agadir to be "rescued". The Panther arrived on July 1st 1911, only to discover that Wilburg hadn't arrived, so the gunboat sat impotently in the bay waiting for him. When he finally did reach Agadir, he was so exhausted from his journey that his only priority was finding a hotel for the night. The next morning he awoke to discover that the Panther had been joined by a second German gunboat, the Berlin. Deciding it was time to go and get himself rescued, Wilburg made his way down to the beach and waved at the ships... who promptly ignored him. Frustrated, Wilburg began to jump up and down and throw a tantrum on the beach - only for the officers of the Berlin to assume he was a deranged native. It was only when Wilburg stood with his hands on his hips and glared at them with silent fury that it dawned on them that this might be the man they were supposed to rescue - because no native would ever stand with his hands on his hips. Wilburg was duly saved from the terrifying prospect of a nice day on the beach. In truth, the entire episode had been intended to warn the French off trying to obstruct German colonization in Africa, but backfired spectacularly when it drew the ire not just of the French, but the British as well.
Worse yet, the incident demonstrated Austria-Hungary's complete unwillingness to back Germany up when push came to shove. Rather than seeking a new ally - i.e. Russia, a rising power with close economic ties to Germany - they tried even harder to enlist Austro-Hungarian support. Ultimately, German support for Austria-Hungary and fear of Russia's growing economic and military power impelled Germany to escalate a war between Austria-Hungary and Russia into a pan-European conflict involving France and Germany as wellnote under the fatalistic logic that war was inevitable (largely because of French desire to retake Alsace-Lorraine) and the odds would only get worse as time went by and Russia became even more powerful - Russia had already matched Germany in artillery by 1914, to say nothing of the size of her trained reserve of manpower as a country with more than twice the population of Austria-Hungary and Germany put together . Neutral but virulently Germanophobic Britain using the invasion of Belgium as a pretext to attack Germany and Germany staging a False Flag Operation to bring The Ottoman Empire into the war against Russia were just the icing on the cake.
At the start, only Churchill and Gray were in support of intervention, and both the leadership and citizenry the U.K. were unwilling to get involved in the war. It was the atrocities which the German army committed in Belgium which finally propelled them to act. Those atrocities were themselves propelled by the Germans not being familiar with the nature of urban combat, where every shot echoed, causing a false believe that the troops were constantly under threat of ambush by native partisans. By the standards of the time, partisans were considered war criminals so those atrocities were considered "appropriate" by the occupying forces.
Publicly in support of intervention. Declaring war on Germany was a fantastic opportunity to destroy another Great Power and make The Irish Question, womens' rights, and labour unrest go away for a bit. Britain had fully intended to make war on Germany in the event of any Franco-German war, including one started by France, for at least three years (i.e. since the second Moroccan crisis of 1911) by then. Claiming it was all done to champion the cause of some foreigners nobody actually cared about was great stuff for keeping the common people quiet, but it would be a grave mistake to assume this was an actual reason. Britain showed what it really thought about 'neutrality' and 'atrocities' with their wartime occupation of non-aligned Greece, their handling of assassinations and rebellion in Ireland ('Black and Tans', anyone?) and 'Amritsar Massacre' of 1919. Reginald Dyer, responsible for the lattermost, retired a national hero.
The two Moroccan Crises of 1905 and 1911. Both also illustrate the major problem with the gunboat approach; you have to have the biggest stick around to pull it off, or you'll be slapped down by those who do.
American exercises off Libya in the 1980s, especially the Gulf of Sidra incidents.
Older Than They Think once you find on a map where the Barbary States were located. The Marine Corps hymn doesn't mention the Shores of Tripoli because of anything they did in the 20th century.
The Barbary Coast states were known as pirates and slave takers until visited in turn by the Americans, the British, and the French at the beginning of the nineteenth century. These three each persuaded them to turn to more gentle ways of life by the use of exceedinglystrongpersuasions.
The crisis also demonstrated the potential for gunboat diplomacy to backfire. The crisis was precipitated by the Chinese military conducting missile tests less than 40 miles from ROC-controlled territory as well as a mobilization of Chinese troops in Fujian province (the province closest to Taiwan) and several live-fire exercises. The actions were intended to scare the Taiwanese populace into not re-electing then-President Lee Teng-hui, who was seen by China as being pro-independence - the crisis actually boosted Lee's popularity in the 1996 election and gave him an outright majority in the polls as opposed to a mere plurality. China has since learned its lesson and hasn't tried anything so radical in subsequent Taiwanese elections.
Perhaps most famously, the diplomatic mission of Commodore Matthew C. Perry (not that one) to the Empire of Japan.
Subverted by his Russian equivalent, Admiral Yevfimy Putyatin who managed to open Japan for Russia after a tsunami destroyed his fleet.
This was only the most famous of several rounds of this trope with Japan; Britain, after an English businessman was murdered for refusing to dismount and pay his respects to a passing noble, sent a squadron to bombard the towns of Kagoshima and Shimonoseki. Part of why Commodore Perry's tactics worked was because a growing faction in the Shogunate were going "Guys, we have got to get some of that for ourselves!"
The final Japanese surrender in World War II was signed on USS Missouri, a battleship. Perry's US flag was brought along for the occasion as MacArthur was a blood relative Perry's.
Subverted repeatedly to its own ultimate detriment by Joseon Korea, which had seen what "opening markets" had done to China and wanted little part of it. The American armed schooner General Sherman was sent to Pyongyang in 1866, ostensibly to open trade relations, only to be destroyed by fireships when the crew refused to accept "no" for an answer. Later the same year, an estimated 800 French soldiers aboard six warships attempted to seize the mouth of the Han River and coastal access to the capital, only to be forced back by winter and overwhelming opposition. Talk of a joint French-American punitive expedition went nowhere, but in 1871, the Americans tried again with over 600 marines and five warships, taking five fortifications along the Han River and managing to only strengthen the regent's opposition to modernization, including new proclamations against "appeasing foreigners." It wasn't until their rapidly-modernizing Japanese neighbours threatened to fire on the capital Hanseong (today Seoul) itself that the Hermit Kingdom was finally forced to open its markets to foreign trade, with Japan, America, and Russia at the forefront.
In order to construct the Panama Canal, US President Theodore Roosevelt encouraged the Panamanians to revolt against their Colombian rulers, promising assistance from the US Navy. The rebellion was successful mainly because the USS Nashville just happened to be in local waters, discouraging the Colombians from sending troops to quell the rebels.
Used without end by both sides during the Cold War with various degrees of success. There were many versions, from troop movements around the border, military exercises that were either intentionally leaked or outright covered by the media, nuclear weapons testing... The who blinks first attitude shared by both sides nearly led to World War III and the End of the World as We Know It, multiple times.
An interesting dueling version: During the 1971 Indo-Pakistan War, the US sent in the Enterprise battle group to threaten India to stop curb-stomping the Pakistanis, only for the Soviets (who were sympathetic to India) to do the same thing. To prevent this from becoming a Pretext for War, the Americans stood down.
The order of the day between North and South Korea: if you don't like how things are going in the diplomatic table, you arrange a "joint military exercise (with live rounds!)" near your neighbor's land or naval border. Sometimes the "training bullets" fly outside the exercise zone, too.
The US and South Korea habitually do joint training exercises near the hot area. When, in 2013, North Korea started one of the worst rounds of saber-rattling yet, the US sent a missile destroyer and a couple of B2 heavy bombers to play, in a show designed to say "careful who you mess with".
Shows of force are not limited to one's adversaries. They can just as much be messages to one's allies: "I will support you in the face of this third country threatening you" is more credible if you have your own skin in the game, like your own soldiers and ships.
As a specific example, take the presence of American soliders in Europe as part of NATO during the Cold War. US foreign policy up through World War II traditionally favored neutrality (at least with respect to Europe) and staying out of potentially entangling alliances and conflicts.note Indeed, the proposed Ludlow Amendment (1937) and later Bricker Amendment (1951) would have made it harder for the US government to do otherwise. Even during the Cold War and the formation of NATO, there was much worry among some in Western Europe that, if Warsaw Pact troops did invade, the US would just leave them to their fate rather than send their own soldiers to die on someone else's land; the US's commitment to using nuclear weapons in retaliation was similarly questioned (why bring The End of the World as We Know It on everyone, including Americans, when not using them would only mean Western Europe gets new management but at least not a nuclear wasteland?). Placing US troops in Europe was at least partly to assauge these fears - it would be far more difficult for Washington to politically justify not getting involved in a Warsaw Pact invasion scenario if American blood had already been shed.
The Berlin Brigade, a US Army contingent that was stationed in West Berlin (the UK and France also had similar contingents), can be considered an example of the previous on a smaller scale. Unification of Berlin was a prized objective of East Germany and the Soviet Union for reasons politicalnote Having a unified capital that went back to the German Empire would give East Germany more legitimacy to its claim of representing all of Germany and allowed communist propoganda to portray the Bonn-based West Germany as an illegitimate puppet (and by extension shame the Western powers supporting it) and praticalnote West Berlin, being so far behind the Inner German Border and having special rules that effectively became legal loopholes for emigration (not to mention how heavily guarded the Iron Curtain was), was a popular destination for many East German defectors, and it wasn't like the Soviets wouldn't consider trying to strongarm the West into giving up West Berlin (c.f., the 1947-48 Berlin Blockade, the tank standoff at Checkpoint Charlie in 1961) - in a hypotehtical Warsaw pact invasion West Berlin would almost certainly be a target. The force wasn't all that large - about 3,000 for the US - and in an actual shooting war they would not have lasted more than a few days to any serious push by Warsaw Pact troops because they would be outnumbered by a ridiculous margin and be immediately cut-off from supplies behind the Iron Curtain. The real point was to make US citizens die in the defence of West Berlin and West Germany so that the USA's isolationists would be unable to oppose war, and make NATO think it was less likely that the USA would abandon them if war broke out.
Both China and America have been sending their magnificent naval fleets to the South China Sea. The PRC, to defend the undersea resources they claim to be rightfully theirs (which is to say, the entire seanote International law puts a country's "EEZ" up to 300 km out from their coastline. The South China Sea dosn't align with the PRC's Coastline at all, and the sheer size of it means that the only way they could legally claim it all (as they do) is by controlling every bit of land that borders it - which is where the not-PRC countries of Vietnam, Malaysia, and The Philippines come in with their pesky independence and legal rights.); the USA, to curb the PRC's claim by protecting the interests of her South-East Asian allies, who under international law have legitimate and universally-recognised (except by the PRC) claims to it.
Employed by the USSR in the so-called First Socialist War (China's punitive war against Vietnam concerning the latter's incursions into China-friendly Cambodia). In 1979, as the PRC wound up its limited offensive upon Vietnam, the Soviet Union - Vietnam's ideological and Realpolitik backers - conducted one of the largest military manoeuvres in its history. More than thirty divisions were airlifted to the Sino-Russian border in less than a week, and the Navy burned through three years of its fuel reserves in the course of a month. Two divisions were actually left in Mongolia after the exercises, as doing so was cheaper than bringing them back. As far as the Soviets were concerned, not to mention the Vietnamese, the Chinese had been scared into submission. The Peoples' Liberation Army's desire to avoid the appearance of caving in to Soviet pressure actually made them want to continue to prosecute the war beyond the (limited and from a military standpoint, stupid) objectives they had been set.
This trope is best summed up by the old maxim (source unknown) "Diplomacy works best when it's backed by credible threat of force."
Iran, under pressure of embargo over their nuclear development, had threatened to blockade the Suez Canal. The US responded by deploying their biggest aircraft carrier to patrol the waters.
Northrop Grumman - the owners of the shipyards where US aircraft carriers are built - actually sell T-shirts and posters with the image of the USS Enterprise from the front and the legend: "90,000 tons of diplomacy."