A maritime flag is a flag used exclusively on boats and other watercraft. Flags are very important at sea, where they can mean the difference between life and death, and consequently the rules and regulations for the flying of flags are strictly enforced.**************Ensigns are national maritime flags flown by ships, at the stern, from a gaff, or from the yard-arm. In some countries (e.g., the United Kingdom, Italy, Russia or Australia) there are distinct naval and merchant ensigns, while in other countries (e.g., United States or France) the merchant and naval ensigns are identical to the national flag flown on land. Ensigns are usually required to be flown when entering and leaving harbour, when sailing through foreign waters, and when the ship is signalled to do so by a warship. Warships usually fly their ensigns between the morning colours ceremony and sunset, when underway, and at all times when engaged in battle—the "battle ensign". When engaged in battle a warship often flies multiple battle ensigns. This tradition dates from the era of sailing vessels. Tradition dictated that if a ship lowered its ensign it was deemed to have surrendered. Masts were targets of gunfire, and the second and subsequent ensigns were flown in order to keep the ensign flying even after a mast hit.