The USS Arizona was a Pennsylvania-class battleship commissioned in the United State Navy in 1916. She went through an extensive modernization in 1929, with new deck armor, boilers, turbines, guns and fire-control. During the surprise Japanese attack on Pearl Harbor, Hawaii, on Dec. 7, 1941, a bomb detonated a powder magazine in the Arizona and the battleship exploded violently and sank, with the loss of 1,177 officers and crewmen. The U.S. made a formal declaration of war against Japan and subsequently all Axis powers. The wreck still rests at the bottom of the harbor and is now part of the USS Arizona Memorial.