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.