A battle ensign is the name given to a large war ensign (flag) hoisted on a warship's mast just before going into battle. In what could become a very confusing situation with thick clouds of gunsmoke the ensign gave additional identification, hence their large size, which for the Royal Navy in the 17th and 18th centuries was 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.