"The United States Navy"
The US Navy had three pre-dreadnought battleships still in service for WWII, the ex-USS Oregon, ex-USS Kearsarge, and ex-USS Illinois. As IX-22, AB-1, and IX-15, they all survived long after the war. The US Navy adopted the prefix "USS", for "United States Ship", in 1907. No official prefix was used before that. "BB" is the designation for "battleship", while "IX" is for "unclassified miscellaneous auxiliary" and "AB" is for "Auxiliary, Crane Ship".
CLICK ON A SHIP"S NAME TO SEE A HISTORY
AND PICTURES OF THAT VESSEL:
USS OREGON BB-3
USS KEARSARGE BB-5
USS ILLINOIS BB-7