To burn your bridges is to do something that permanently closes off options for retreat or reconciliation. Quitting a job while insulting the management burns your bridges with that employer. Publicly cutting ties with a country, organisation, or person in a damaging way burns your bridges with them. The phrase implies a point of no return — you cannot cross back over what you have destroyed.
The origin is military and ancient. Commanders throughout history deliberately destroyed bridges, boats, and transport behind their advancing armies to prevent retreat — removing the option of withdrawal forced troops to fight with maximum commitment or die. Julius Caesar was said to have used this tactic in Gaul. William the Conqueror reportedly destroyed his fleet after landing in England in 1066 to leave his troops no route of escape. Napoleon ordered bridges burned in his retreat from Moscow to slow the pursuing Russian army.
The military tactic was well documented in classical and medieval history. The English metaphorical phrase emerged in the 19th century as historical military literature became widely read and the image gained currency in civilian life. Today it applies most often to relationships, careers, and social alliances — the bridges being not physical crossings but lines of communication, goodwill, and return.
Not necessarily. Sometimes a decisive break is necessary and liberating. Some career moves, relationship endings, and personal reinventions require burning bridges to commit fully to the new direction. The phrase itself is neutral about whether the action was wise — it simply describes finality.
The deliberate military version — burning bridges to deny yourself retreat — is sometimes framed positively as commitment. Hernán Cortés scuttling his ships before the conquest of Mexico is often cited as a bold leadership decision, not just recklessness.