The phraseological phrase “to burn ships” implies a situation created by some act that makes a return to the past absolutely impossible, cuts off the path back.
Any stable allegorical phrase did not immediately become one. If they speak of "burning ships" in a figurative sense, it means that someone once burned quite real ships, and this was done for various reasons.
The burning of ships implies the impossibility of returning. The path from which no one returns and never is death.
In many mythological traditions, a river appears that separates the world of the living from the world of the dead. Among the Greeks and Romans, the dead were served by the afterlife carrier Charon, but among other peoples, people traveling to the kingdom of the dead had to rely only on their own strength. Therefore, there was a custom to bury the dead in boats, boats and even large warships, if the deceased was a noble warrior or prince. An echo of this tradition is a modern coffin, vaguely resembling a boat in shape.
The funeral boat could be buried in a mound, let it flow along the river, but there was also a tradition of burning in a boat - after all, the fire element was also considered sacred, therefore, it helped the transition to the other world.
But although the ships were burned at funerals, this phraseological unit owes its origin not to funeral rites, but to war.
Generals who burned ships
Even in ancient times it was noticed that the most decisive thing is the person who has nothing to lose. Even the bravest warrior can succumb to temptation at a critical moment and flee from the battlefield to save his life. If the only possible alternative to death is victory, such a temptation will not arise. A victory-or-death warrior is especially terrifying to enemies and effective in battle.
The commanders knew this and tried to artificially create such a situation for their soldiers. For this, they could use, for example, detachments, whose duties were to kill those who fled. If the army arrived at the battle site by water, they acted easier: they destroyed the ships. In this case, the soldiers could return home only by capturing enemy ships or building new ships on the spot, which was also possible only in case of victory - the deserters had no chance. The commander could have no doubt that his people would fight to the last drop of blood - their own or the enemy's.
In an era when all ships were built of wood, the easiest and most affordable way to destroy them was to burn them. This was done, for example, by the king of Sicily, Agathocles of Syracuse, who landed in 310 BC. in Africa. William the Conqueror also burned the ships, landing in England in 1066.
The ships could not only be burned, but also flooded. This was done in 1519 by the Spanish conquistador Hernan Cortez, who landed on the territory of modern Mexico. Despite the stories of fabulous riches, the Spaniards were afraid to go inland, and Cortez deprived them of their choice by sinking all 11 ships.