"Burning the/your ships/boats" means doing something that makes it impossible for yourself to turn back, especially if it is done wilfully and without necessity. The figure of speech derives from legends about conquerors who supposedly, upon landing their army in enemy country, ordered the invasion fleet to be burnt. Most people today have heard this tale about Hernán Cortés, but it is in fact centuries older than Cortez. "Burning the bridges" has the same meaning.
The assumed benefit of such an act is that everyone on the team-whether it be an actual army intent on conquest, or any party pursuing a risky undertaking–will show maximum commitment if they know that retreat is impossible. There isn't any use in holding back or playing it safe when there is no exit option to fall back on. Desertion or mutiny is futile if there is no hope of escape. Dissenters are silenced when there are no choices left to argue over, and everyone's best hope of survival lies in cooperating for the common success. Once the Ships are Burnt, it's do or die for everyone-succeed, or face death or captivity.
Or that is the theory. While tales of this type are a favorite of motivational trainers, who always focus on how "cutting off your retreat" will set free unknown potentials, there are only few historical examples of things like this actually happening, and then usually not for the exact same reasons. Also contrary to what motivational trainers like to suggest, it is not actually a guarantee of success.
Depending on the situation and the kind of enterprise at hand, there are many ways of Burning the Ships:
Throwing away vital supplies, like food or fuel.
Destroying irreplacable equipment needed for the return journey.
Intentionally leading your troops into a tight spot from which there is no way of escape without fighting.
Giving your position or your plans away to the enemy, so they will block your exits.
Destroying the radio or other means of communication needed to call for help.
A group of people that intends to commit treason of some sort may send a message confessing their defection to the betrayed faction, making it impossible for anyone who gets cold feet to turn back to their old master and evade punishment.
If actual ships are destroyed, burning is the preferred method. Obviously there are other ways to wreck ships, but burning is the most picturesque.
An act like this can be unilaterally ordered by a leader, or agreed on as a collective decision. But it always hints at internal conflicts within the party that is thus committed to a common goal: Usually it is done precisely because the initiatiors of a Ship Burning do not trust in the loyalty or the morale of the rest of the group in the face of danger. Objecting to a Ship Burning is hard, as it may lead to being branded a coward or even traitor. Burning the Ships may be nothing less than a stratagem to coerce the group into a course of action they would not have chosen from their free will.
Characters who order or initiate a Ship Burning are always reckless and uncompromising, and often morally ambivalent: Shining heroes do not need to force their followers to fight, or put the lives of their companions at unnecessary risks; on the other hand, even bad guys can earn some respect from the audience if they show they have no backup plan in the case of defeat. Characters who Burn the Ships are often Anti-Heroes, Anti-Villains, or Villain Protagonists.
This trope often leads up to a Big Badass Battle Sequence, which will more than likely end in a Last Stand.
Compare Cornered Rattlesnake, which is non-voluntary. Contrast Let The Past Burn, which is mostly a symbolic action on an individual scale. An employee quitting job in a way that makes sure they can't ever go back again is Take This Job And Shove It. Throw the Sheath Away is a distant relative.
Anime and Manga
Fist of the North Star: While in the process of mourning the fallen Hyui, Shuren, one of the Five Chariot Stars, incinerates his army's fortress as a memorial to his fallen comrade and as a means to force his men to attack the killer, Raoh. Shame that it does very little to help him survive his fight with Raoh.
Berserk: In the Battle of Doldrey, Griffith positions himself and the portion of his army that he expects to face the largest part of the enemy force with their backs to a river and no way to retreat. He does this not only to motivate his own men, but also as part of a Batman Gambit: Cornered and outnumbered, his force presents a tempting target that succeeds in drawing the enemy forces out of their castle, which is promptly captured in a sneak attack by a small flanking force.
Fullmetal Alchemist: When setting out on their journey, the Elric brothers Ed and Al burn down their childhood home so there will be no turning back.
In the Polish comic series Kajko i Kojosz, Hegemon, the leader of the villainous Banditknights, was always afraid that his men would chicken out at the last moment and not follow him into battle. Thus he would always try to find a way to prevent this by destroying any means of retreat. The Genre Savvy heroes would realize this and use it against him. In one instance the Banditknights built a siege tower that would get them onto the town's walls. Once all of them were inside, Hegemon set fire to the bottom of the tower so everyone had to exit through the top. However, during the previous night Kajko and Kojosz sabotaged the tower by shortening the ramp at the top so all the Banditknights ended up falling into the moat instead.
At the end of The Bounty Fletcher Christian has the HMS Bounty burned, to make sure the mutineers are committed to living on Pitcairn Island and to prevent anyone from trying to get back to Tahiti or England. (Real Life demonstrated how this tactic can backfire. When an American whaling ship stumbled on the island 19 years later and solved the mystery of the lost HMS Bounty, only one mutineer was left alive, along with several women and children. The other mutineers and the Tahitian men that went with them had all killed each other off.)
The 1935 version of Mutiny on the Bounty also has Christian burning the ship, as happened in Real Life. The 1962 film puts an odd and fictional twist on it, by having the crew burn the ship after Christian decides to go back to England.
In the first Jaws, Quint destroys the radio when Brodie tries to call for help, and later appears to deliberately burn out his engine so they can't escape their final confrontation with the shark.
In the film of The Hunt for Red October, Marko Ramius, captain of a submarine carrying nuclear missiles, sends a letter to the CO of the Soviet Navy stating that he and his command staff are defecting. When his staff officers ask him why he did it, he cites the example of Cortes' destruction of his ships.
Invoked in Gattaca: The movie features two brothers, Anton (born with genetic enhancements) and Vincent (without). Both brothers throughout their childhood competed in a game of "chicken" where they would swim out as far out to sea as possible with the loser being the one who turns back first, which Vincent consistently wins despite Anton's genetic advantage. As an adult Vincent reveals his secret to Anton: he never saved any energy for the swim back. This parallels Vincent's quest to become an astronaut despite his genetics and thus society standing in his way via sheer determination and audacity.
In The Shining, Jack Torrance, slowly being possessed by the evil spirits in the snowed-in Overlook Hotel, disables the ham radio (the family's only means of calling for help) and the snowmobile (their only means to leave the hotel).
From Aguirre, the Wrath of God: After promoting Don Fernando de Guzmán to 'Emperor of El Dorado', Aguirre makes Carvajal write a letter to King Philipp of Spain which declares not only their defection from Spain, but also the "overthrow" of the House of Habsburg and the "dethronement" of Philipp. The letter is kept by Aguirre, who in this way makes sure that Guzmán and the rest cannot bail out of their rebellion, as the letter is incriminating proof of their complicity.
Aguirre: Fortune smiles on the brave and spits on the coward. Let's sever our ties with Spain and crown Don Fernando de Guzmán Emperor of El Dorado.
Sun Tzu advises this as one of his stratagems in The Art of War, but for the same reason warns against forcing an enemy into a situation where it appears his only option is to fight to the death. Instead he advises leaving an apparent escape route to encourage flight. A fleeing enemy is more easier to kill, after all.
The Silmarillion: After the Noldorin Elves led by Fëanor have crossed over from Aman to Middle-earth on the ships they stole from the Telerin Elves, Fëanor orders them to burn all the ships. He does this to prevent any of his followers from returning to Aman, but also to make sure they cannot help the rest of the Noldor who follow Fëanor's brother Fingolfin get to Middle-earth.
In Cursor's Fury, book three of the Codex Alera, Sarl, the Canim commander, burns the Canim fleet in order to prevent the warriors under his command who are there under duress from fleeing back home. The invasion was ordered by priests of two castes who dislike each other passionately.
In Belgarath the Sorceror, Riva orders the ships that carried the settlers to the Isle of the Winds burned. He knows it will take a lot of hard work to build the fortress-city, and he doesn't want anyone deciding it's too much work and leaving.
The Hunt for Red October: Marko Ramius, captain of a submarine carrying nuclear missiles, sends a letter to the CO of the Soviet Navy stating that he and his command staff are defecting. When his staff officers ask him why he did it, he says the knowledge that there is no turning back will strengthen their motivation and commitment.
In Honor Harrington, the original colonists to Grayson wrecked their starship's cryonics equipment, ensuring that it would be impossible to return to the "sinful" Earth. They didn't wreck the whole thing, though, which is fortunate because it turned out that the planet was basically one huge Superfund site and there's no way they would have survived without the ship's resources.
In Redwall: When Cluny the Scourge arrives in Mossflower, he press-gangs all of the local vermin into his cause and orders his rats to smash the new conscripts' houses, so they will have nothing to return to if they desert him.
Julian did this believing that his victory was assured by the gods. He was wrong. One character described it as the beginning of the end: "Nothing went right again."
In "Paradise", Sisko and O'Brien come across a group of space Luddites who crash-landed on a planet ten years ago, and since then have thrown away all their electronic technology, thus forsaking any chance to call for help. It turns out the leader of the group and her son had secretly sabotaged the ship so it would crash and are keeping a technology-blocking device going so that nobody on the planet can use any technology even if they wanted to.
In "Hippocratic Oath" a Jem'Hadar commander discovers that he has lost his genetic addiction to Ketracel White which his race has been bred to have in order to make them loyal to the Founders. He takes his platoon to an empty planet because he thinks the plants there have cured him, and then destroys both his ship and most of their supply of Ketracel White to get them off the stuff too. But it turns out he's the only one who is affected, and the rest of the crew develops withdrawal symptoms.
In The Twilight Zone episode "On Thursday We Leave For Home", Captain Benteen tries in vain to destroy the rescue ships from Earth because he wants to remain in control of the people on the asteroid.
In Halt and Catch Fire Joe deliberately informs IBM that Joe and Gordon, as Cardiff Electric employees, have reverse engineered the IBM PC BIOS code. IBM sends in an army of lawyers and Nathan Cardiff is left with two choices: fully commit his company to the PC clone project Joe is advocating or get sued into bankruptcy by IBM. Everyone is furious at Joe but in the end he gets his way. This is then subverted when we realize that the project's failure will ruin everyone except Joe. He forced everyone else to take a high personal risk and commit fully to the project, but due to his father's connections he can walk away at any time and resume his old life.
Manowar's "Heart of Steel" features a few lines about just this trope.
Burn the bridge behind you Leave no retreat There's only one way home Those who laugh and crowd the path And cut each other's throats Will fall like melting snow
Christian music artist Stephen Curtis Chapman has a song titled "Burn the Ships", which references the Cortez tale. It's a metaphor for not going back to your old life once you've made a change.
My Brightest Diamond references this in the song "Escape Routes", where it's a metaphor for choosing love over apathy.
Let's close off all our escape routes Let's not put it off tonight Let's close off all our escape routes We can have it all tonight
Mythology and Tradition
After crossing the Huang He into hostile Quin territory in 208 BC, Xiang Yu of Chu supposedly ordered his army to sink the boats, as well as to pack only supplies for three days and to destroy the rest, along with the cooking utensils. This meant that they could neither go back, nor avoid starvation except by conquering the supplies of the enemy. The traditional wording of the order, "Break the kettles and sink the boats!" (破釜沉舟), are a Chinese idiom.
A legend about Tariq ibn Ziyad, the Berber general who conquered the Visigothic kingdom of Spain, says that he had his fleet burned after landing his army at Gibraltar in 711. This version is first mentioned only in the 12th century by the geographer al-Idrisi.
Nibelungenlied (adventure 25): After ferrying the entire Burgundian army across the Danube, Hagen hacks the boat to pieces and casts them into the river. Asked why he did that, he replies they will not need the boat again and that he wishes that any deserters who might turn back should drown in the river. A little later he reveals that three river-women have already predicted that they will all die in Hunland.
In the "Greenlandic Lay of Atli" of the Poetic Edda, the Niflungs do not fasten the boat in which they have rowed to Hunland, so it will presumably be driven away by wind and waves. This is a hint that they already expect that they will not return.
According to The Battle of Magh Tuireadh, the Tuatha Dé Danann "immediately broke and burnt all their ships and boats" upon landing in Ireland to challenge the Fir Bolg for one half of the island.
Styrbjorn in "The Tale of Styrbjorn" has his fleet burnt after sailing up the Fyris River to Uppsala to challenge his uncle Erik for the kingship.
He burned all the ships on which he had come there, because he believed his men would not be so quick to flee if there was no way of getting away from there.
In the history of the Tuala Morn setting of Fantasy Hero, the ancestors of the Tualans were refugees hunting for a new homeland. Once they decided to settle in Tuala Morn, their leader scuttled their ships as a sacrifice to the sea gods, thanking them for their aid.
In Warcraft III, Prince Arthas Menethil leads his troops to Northrend to capture Mal'Ganis. While Arthas is out of the basecamp, a messenger from King Terenas arrives with orders for the men to retreat. When Arthas returns to find his men preparing to leave, he has their boats burnt, thus forcing them to go on while blaming it on the mercenaries he hired for the job.
SpongeBob SquarePants: In "Clams", Mr. Krabs enlists SpongeBob and Squidward to help him to get Krabs' millionth dollar back from the clam that ate it. As motivation to catch the clam (and in an allusion to Moby-Dick), Mr. Krabs nails a sandwich to the mast of the ship—and then throws the boat's fridge overboard, so that no one may eat until the clam is captured.
"Now understand each other. Nobody eats until we get my millionth dollar back."
After sailing from Cuba to Mexico in 1519, Hernán Cortés had eight of his eleven ships beached and disassembled. Cortés, who acted in defiance of the orders of his superior, governor Diego Velázquez of Cuba, had just before put down a mutiny of soldiers loyal to Velázquez and feared that the same might happen again as long as the ships allowed a fast return to Cuba; furthermore he could reinforce his march inland with the crew and the equipment of the dismantled ships. The details of the decision process are murky: While Cortés himself wrote to Emperor Charles V that he alone gave the orders under the pretense that the ships were no longer seaworthy, sparing only the ships the crews of which he considered reliable, the eyewitnesses Bernal Díaz and Andres de Tapia later claimed that the destruction of the ships was decided after a general discussion. Francisco de Montejo and Alonso Portocarrero, messengers of Cortés that were sent to Spain immediately after the event, claimed that the ships really had been unseaworthy. The misconception that Cortés burned (all of) his ships is old, being first mentioned in a letter from 1546.
At the Battle of Ferrybridge, a minor battle of the Wars of the Roses, the Earl of Warwick, as vanguard commander of the Yorkist army, killed his own horse to prevent a panic among the Yorkist troops, supposedly commenting this act with the words "Flee if you want but I will tarry with he who will tarry with me!" The battle ended with a Yorkist success, though the impact of Warwick's act on the outcome is unclear. Although Warwick did not know it at the time, the Lancaster leaders had abandoned the attack.