Naval ensign
A naval ensign is a flag used by warships to show which country they belong to. Sometimes a naval ensign is called a war ensign.
A naval ensign flies from the back of a ship. Some countries use their national flags on warships as their naval ensigns. The United States is an example of a country that uses its national flag instead of a naval ensign. Some other countries have a special naval ensign different to its national flag. Britain is an example of a country which uses a special naval ensign different to its national flag.
Russian Project 775 landing ship Korolev. Note the Russian naval jack at the front and naval ensign at the rear.
Austria-Hungary (1915–1918) - never formally flown by the navy