In days of yore when men fought in sailing ships, a naval captain could only signal his intention to surrender his vessel by ‘striking the colours’—that is, by ordering the ship’s flag to be lowered. In the heat of a naval battle, however, the rope holding a ship’s flag could easily be shot away. The flag would then come fluttering down leading both the crew and the foe to conclude (wrongly) that the captain was surrendering. There was only one effective remedy—‘nail’ the flag to the mast before the shooting started. This ensured that no false signal of surrender could be made as long as the mast itself was still standing. Of course, it also meant that no signal of surrender, even an intentional one, could ever be made. The expression ‘nailing one’s flag to the mast’ has passed into modern usage as a way of saying that no surrender or compromise is possible.
The technique was not limited to naval warfare. Both William the Conqueror (attacking England in 1066) and Hernán Cortés (attacking the Aztecs in the early 1500s) famously burnt their ships on the beach. This was a not-very-subtle way of announcing to the troops that retreat was simply not possible. Julius Caesar, prior to the battle of Bibracte in Gaul in 58 BC, is said to have ordered his soldiers to abandon their horses. The message? No Roman would be leaving the battlefield prematurely and none would be leaving at all if the Roman army was not victorious.
The purpose of nailing a flag to the mast or burning boats on a beach is thus deliberately to foreclose options. In the jargon of modern game theorists, it is an overt method of reinforcing the ‘credibility’ of the only remaining option—victory. The game theorists refer to this as a ‘tying hands’ or ‘burning bridges’ strategy.