Battle ensign

A battle ensign is the name given to a large war flag which is flown on a warship's mast just before going into battle.

The flag identified the allegiance of the ship in what could be a very confusing situation, with thick clouds of gunsmoke obscuring the ships in action, hence the large size of these ensigns typical for the Royal Navy from the 17th to 18th centuries of about 20 by 40 ft (6.1 by 12.2 m). It was commonly accepted that so long as a ship flew its ensign it was an active participant in battle; prior to action it was an acceptable ruse to fly a false flag.

If a ship surrendered then it would take down its ensigns (which was known as striking the colors). This is also the origin of the phrase "To nail one's colours to the mast", showing a determination to fight on and never surrender. In practice, warships would fly more than one battle ensign, so that if the flag was destroyed or brought down during the fighting there would be no confusion. Conversely, keeping the flag flying even though the ship might appear to be past fighting was a sign of determination rather than foolishness. The German battleship Bismarck continued to fly its battle ensign even after its gun batteries had all been silenced by British shells, and it sank with the ensign still up.