USNS Comfort (T-AH-20) is the third United States Navy ship to bear the name Comfort, and the second Mercy-class hospital ship to join the U.S. Navy's fleet. The USNS prefix identifies the Comfort as a non-commissioned ship owned by the U.S. Navy and crewed by civilians from the Military Sealift Command (MSC). In accordance with the Geneva Conventions, USNS Comfort and her crew do not carry any offensive weapons. Firing upon Comfort would be considered a war crime as the ship only carries weapons for self-defense. Like her sister ship USNS Mercy, Comfort was built as a San Clemente-class oil tanker in 1976 by the National Steel and Shipbuilding Company. Her original name was SS Rose City and she was launched from San Diego, California.