Emirate of Abu Dhabi
From 1820 Britain imposed treaties or truces with the ruling sheikhs and all Gulf Sheikhdoms were requested by the British to include the colour white in their plain red flags in order to signify that they had signed the Anti-Piracy Treaties. Abu Dhabi however readopted the plain red flag in 1833, but returned to a white-bordered flag in 1835, when a new treaty was signed. A red flag with a white stripe at the hoist was introduced in the 20th century although the plain red flag was still used on land. In 1958 the present flag was introduced: red with a white canton.