It can also be known as a war ensign. A large version of a naval ensign which is flown on a warship's mast just before going into battle is called a battle ensign. An ensign differs from a jack, which is flown from a jackstaff at the bow of a vessel.
Most countries have only one national flag and ensign for all purposes. In other countries, a distinction is made between the land flag and the civil, state and naval ensigns. The elaborate British ensigns, for example, differ from the flag used on land, the Union Flag, and have different versions of plain and defaced Red and Blue ensigns for civilian and state use, besides the naval ensign (White Ensign). Some naval ensigns differ in shape from the national flag, such as the Nordic naval ensigns, which have 'tongues'.