The Big Bad and the Hero meet in peace. Whether the intent is malicious or benign, both sides seem willing to talk it out, at least for now. And anyways, you can't just lop off somebody's head during parley, right? Eh... right?
Apparently you can, considering the fact that somebody involved in the parley has just busted out swords, guns, or a Humongous Mecha. Both sides can pull one of these, though it usually happens when a Mook from one side of the conflict goes to negotiate with the other sides. There are exceptions, however, where many members from both sides participate. In this case, somebody pulling this trope can spark an all-out Climactic Battle Resurrection, resulting in a Nice Job Breaking It, Hero if the hero was aiming for peace. Villains (or Anti Heroes) invoking this trope tend to be Magnificent Bastards.
In a series on the cynical end of the Sliding Scale of Idealism Versus Cynicism, a character that does this is either being Bad Ass for silencing the enemy, or is just being really stupid. Seeing as pulling this trope tends to cause war to break out, there aren't many idealist series with this in them, but characters that do invoke this trope tend to be just incredibly stupid.
Note that, in the long term, regardless of who initiates this trope or why, the main accomplishment will be that the other side simply won't trust them to negotiate in good faith. Which might be good (albeit horrifically immoral) if you can completely wipe out the enemy in this one attack, but will absolutely come back to bite you in the butt later if the enemy has the upper hand.
Contrast and compare with Shoot the Messenger, in which a messenger, who comes in peace, but only to deliver a message, is killed. The two tropes can overlap, as well: if the victim of the invoker of this trope delivers a message and is negotiating, it is both tropes at once.
See Also: I Surrender, Suckers, Gunboat Diplomacy.
Danzo was going to do this in Naruto, but was interrupted by Sasuke busting in.
In The Order of the Stick prequel book Start of Darkness, we see that this is how The Dark One ultimately met his end: he was murdered while attempting to negotiate a peace settlement with the human, dwarven, and elven kings. Rather than ending the war, it made things far worse, as the goblins swarmed upon their enemies, inflicting huge losses in vengeance for their fallen warlord, who as a result Ascended to Godhood.
In the Sinister Dexter story "The Why-Shaped Cut", leaders of the global criminal syndicates meet in The Reef to discuss how to divide up Downlode after the war between Senor Apellido and The Mover ends. When John Crash discovers that Carrie Hosanna is planning on betraying the rest of them and seizing Downloder for the Mangapore Yakuza, he starts firing, and all Hell breaks loose.
The title characters in the Knights Of The Dinner Table have had their PCs do this at least once, while parleying with some orcs. Both Sara and B.A. Felton were not pleased by this.
Helga: Where are you going? Hägar : To make peace with the English. Helga: If you are making peace, why do you need all the weapons? Hägar: Well, we have to negotiate first.
Films — Live-Action
This is played with in Pirates of the Caribbean: At World's End. One pirate shoots another for questioning the pirate code. However, nothing really major happens — the dead pirate was a nobody, and none of the assembled pirates really want a fight to break out at their meeting. A fight breaks out anyway. As Captain Jack Sparrow explains, "This is politics."
In the famous This is Sparta scene, Leonidas is essentially doing this. The Athenians reportedly did it as well. Based on a Real Life example, where when Xerxes' father Darius' messenger demands earth and water as tributes, the Spartans tell them to "dig them out themselves." Athenians did the same. Sparta shoved them into a well, Athens off a cliff. Everybody now:
Messenger: This is blasphemy! This is madness! Leonidas: Madness? This! Is! Sparta! (punts messenger into pit)
Later in the movie, Leonidas mentions that he hopes Xerxes is dumb enough to try this, saying that if they assassinate him during parley, all of Greece will go to war. Regicide during parley would prove to all Greeks that the Persians can't be trusted.
In The Fifth Element, Korben Dallas negotiates by shooting the leader of the Mangalores, knowing that the rest of them will give in.
Dallas: Anyone else want to negotiate? First Mate: Where did he learn to negotiate like that? President:I wonder. (glares at General Munro, who looks uncomfortable)
Inferred to have happened in Gladiator, as the Roman negotiator is returned headless by the barbarians.
In the extended The Lord of the Rings films, Aragorn answers the Mouth of Sauron's demands and insinuations by beheading him with Andúril. In the books, he is merely sent off in a rage; in the theatrical cut, the negotiation does not appear at all.
Obi-Wan: You were right about one thing, master: The negotiations were short.
The Trope Namer is from Attack of the Clones, as mentioned above. Incidentally, this scene was improvised by Hayden Christensen and Natalie Portman, which explains why the dialogue is less stilted than in the other love scenes. The Call Back to the scene during the arena battle ("You call this a diplomatic solution?", "No, I call it aggressive negotiations.") was written afterwards.
Braveheart: William Wallace kind of does this when he angers the English generals when they are parleying to start the first battle. Only fitting, since the English had hanged William's father and some of his compatriots after pulling this stunt when William was a boy.
Men In Black: This is how the Arquellians negotiate. First step is to deliver an ultimatum. Next, they fire a "warning shot" at an uninhabited area (in this case a heat beam at Earth's ice caps). Finally, if the demands are not met within a galactic standard week (one hour), you can say goodbye to Planet Earth.
In Halo: Contact Harvest, a nervous Grunt attacks a marine during a diplomatic meeting and starts the entire Human-Covenant war. The "negotiations" involved the Brutes demanding the humans hand over the planet with everything on it. There was not way this was going to end well.
In one of the Myth Adventures books, Skeeve is parleying with the head of the opposing army when suddenly he realises the opposing army has been moving into position to attack him while he's distracted by the peace talk. He complains that this is a breach of protocol, and is informed that yes, it is, but it also works extremely well.
In Mission of Honor, Honor Harringtongoes to Haven to negotiate a peace settlement, backed up by Eighth Fleet, with the explicit threat that the Havenites can either negotiate, or get their navy blown out of space. Although that's really Gunboat Diplomacy rather than Aggressive Negotiations.
There are actually a few examples in the Bridge Trilogy by William Gibson, most noticably in the second book between Eddie, Maryalice, Chia, and Masahiko. It doesn't help when Zona Rosa gets involved.
Harry Dresden does this from time to time, most notably at the end of Grave Peril when his girlfriend is kidnapped by the Red Court. The war he started over the matter only ended nine books/years later, when he indirectly killed every single vampire of the Red Court.
This is also a trait of the Order of the Blackened Denarius, to the point where Dresden only agrees to a meeting with them because he knows it isn't in their best interest to attack him just yet. He arranges to have backup nearby in case he's wrong.
Invoked but ultimately subverted by Petyr "Littlefinger" Baelish. He meets with the Lords Declarant, lords of the Vale who want to remove him from his position of Lord Protector. He deliberately angers them until one of them draws a sword, which gives Littlefinger a good enough reason to send them away. Later on in the chapter, it's discovered that the guy was actually working for him all along and the whole thing was just an act in order to earn the trust of the other Lords.
Similarly, Catelyn and Jaime hash out a prisoner exchange agreement while he's chained to a wall and she's holding a sword to his chest — after she's already gotten him very drunk. Looking back on it the next day, he actually finds it hilarious — which is a good thing, because for a Lannister, the Rule of Funny is a much more binding law than a sworn oath, and seems to actually be a big factor in Jaime deciding to keep the promise after all.
After Feanor's death in The Silmarillion, his son Maedhros receives envoys from Morgoth offering a truce and the return of a Silmaril. Both sides try to use this trope: Maedhros brings a large party to the appointed place, but "Morgoth sent the more and there were Balrogs" and so overpowered him.
The beginning of the new Battlestar Galactica. There's no actual negotiations at all: the Cylons, after years of not showing up the annual diplomatic meeting, show up and kill everyone with barely a word.
This also happens in the beginning of the original (1970's) Battlestar Galactica. Count Baltar arranged a peace treaty between the 12 Colonies and the Cylons. The Colonies sent all 12 Battlestars to the conference, leaving the Colonies completely undefended. The Cylons carried out a massive attack on both the Battlestars and the colonies, almost completely wiping out both. The battlestars would have had a chance, if Baltar hadn't sabotaged most of the ships and insisted on keeping the Vipers in the hangar bays.
In one episode, a mediator beams down to a planet which has been at war for hundreds of years with his interpreters (he's a deaf-mute). One of the Mooks on one side is against peace talks and kills the interpreters. You have to question the intelligence of this move.
In a couple of other episodes, Spock defends his frequent use of "cowboy diplomacy" when Picard challenges him on it.
One episode of MacGyver features the very careful aversion of this trope: Mac acts as a go-between for two groups who recognize the need for peace, but can't be together for more than a few minutes without hurling insults, at the very least. He keeps them apart by putting them in comfortable suites at opposite ends of a skytram, and relays only written materials.
In Doctor Who, when the Cybermen refuse to answer Rory's demand to know the location where the Silence were holding Amy prisoner, the Doctor blows up the entire Twelfth Cyberfleet in the distance, to show that they were not messing around.
Myths & Religion
In the King Arthur myth, his final battle with Mordred started this way. Neither side trusted the other, and brought plenty of heavily armed soldiers along to the negotiations. The fighting started when one soldier, bitten by an asp, drew his sword to kill it. Both sides had been warned to expect treachery, and responded immediately. Due to the confusion and disorganization, both sides were essentially wiped out.
Quite likely to happen whenever the player characters in any tabletop RPG attempt diplomacy, because there's almost always at least one player who thinks negotiation is boring and would rather have a big fight.
A glitch in the Exalted ruleset, in which physical combat automatically trumps social combat, means that a surprising number of the more insane player characters respond to attempts at mental influence with a daiklave. One of the Dawn Solution Ink Monkeys Charms was particularly extreme, allowing you to hurl sword blows across the world in response to negotiations by letter. (Of course, given that Exalts can actually write letters that will kill you, this does make sense in a sort of psychotic way.)
Radiata Stories was the scene of a trade dispute between the humans at Radiata and the dwarves at Earth Valley. Cross suggested sending knights to 'improve their negotiating position' and its implied this trope was his plan all along.
The Renegade-unlock sidequest in Mass Effect has Shepard sent to negotiate with a self-styled warlord. Said warlord's negotiation style is to start by insulting Shepard, and then make several increasingly unreasonable demands, and becoming hostile if Shepard even questions the demands. At any point during the "negotiation," Shepard has the option of getting fed up and attacking the warlord, which was Admiral Hackett's idea in the first place.
Almost all ways of solving problems nonviolently using renegade options, especially in Mass Effect 2, such as getting past a guard, or having someone reveal information. Sometimes it crosses into Badass Boast territory.
MechWarrior 4: Mercenaries has a mission where player is asked to stand honor guard during the peace talks. It doesn't take long for the enemy army to suddenly bust in with a large group of mechs, and the player is asked to help protect the peace delegates. Brought your most glamorous, but useless in combat mech with you? Too bad.
Suikoden III opens with uneasy peace negotiations between the Grassland clans and the Zexen Confederacy, with Hugo delivering a message to the capital, only to get jerked around, ignored, and ultimately attacked when the Jerkass Zexen Council decides he'd make a good hostage. Escaping that, he makes it home just in time to see his home being burned to the ground.
Ratchet & Clank weapons sometimes imply this trope as a pun — notably, The Negotiator rocket launcher, and it's upgraded form, The Arbiter. Said to quickly conclude legal disputes across the galaxy!
In the Touhou series, any disagreement is settled with a danmaku duel - even such petty things as whether to use red or white miso for a hot pot. Yuyuko seems to like inserting an obligatory Boss Battle into a scene that would otherwise have ended peacefully.
In the the backstory of Star Wars: The Old Republic, the terms of the Treaty of Coruscant that ended (for now) the war between the Galactic Republic and the Sith Empire were essentially dictated to the Republic by the Sith in this manner. After taking control of much of the galaxy by force, the Sith asked for an armistice and a negotiated end to the fighting. The fighting did stop, but only temporarily; during the negotiations on Alderaan, the Sith launched a sneak attack on the Republic capitol of Coruscant and took control of it, forcing the delegation on Alderaan to accept a treaty whose terms were highly favorable to the Sith Empire. The plot for the Karraga's Palace operationnote raid involves this trope as well.
In Sacrifice, playing Persephone's campaign leads to this as all of her 'homeland assaults' on the other gods start out as diplomacy missions that go sour when the other party tries to kill you. So you have to kill them instead to leave.
In the DM of the Rings, the unnamed DM becomes rather upset at the heroes for killing Saruman, Grima, and the Mouth of Sauron in parley.
Aragorn: Yeah, let's speed this up. (kills the Mouth of Sauron) DM: What? You attack him? During parley? This is the third time you've killed someone during negotiations! Legolas: And they keep falling for it! It's hilarious! DM: You're supposed to be a king! Can't you at least pretend to be one for a few seconds? Aragorn: If I hadn't shot him Legolas would have. Legolas: He's right, too. I was just about to announce my attack.
Darths & Droids: Naturally, Jim is fond of this trope. Although he claims to need a laser blaster to properly negotiate, because the lightsaber's reach isn't good enough.
Problem Sleuth: Spoofed; "Sleuth Diplomacy" is only an increasingly indefensible euphemism for canned whoop-ass. Solitudinem faciunt, pacem appellant, and the only time he actually has to negotiate he cheats.
In Goblins, Thaco and Goblinslayer meet in a parley. Goblinslayer plans from the very beginning to kill Thaco instead of negotiating. However, Thaco uses Goblinslayer's pride to his own advantage by challenging him to a single combat, preferably somewhere everyone can see them, causing him to be removed from the place where the actual battle was going on.
Optimus: When Predacons talk peace, it just means they need time to reload their weapons. Megatron: Under normal circumstances, yes.
Colonial powers throughout the nineteenth and early twentieth centuries commonly used this ploy to draw native leaders out, only to capture or kill them.
Asking for negotiations as a ploy to draw them out and slaughter them is a very old tactic. For example, the Romans did it to Lusitania after the last Cartheginian war. The Romans promised them that if they would surrender peacefully and come hand in their weapons, they could be buddies. About 20,000 Lusitanians were slaughtered. This backfired horribly, because a guy named Viriathus survived it and proceeded to very successfully wage war against Rome until he got betrayed and murdered by some of his own people.
Considering how often negotiations come at the end of a war, this is a very common trope in real life.
The Mongols were renown in ancient times for their aversion of this trope; they believed very strongly in Diplomatic Immunity for both sides of the equation, and if they called you out to negotiate that was all they were going to do (for today). The Mongol Empire ended up destroying one of its neighboring civilizations utterly for mistreating a messenger.