All three ships spent the bulk of their peacetime careers in the Pacific Fleet; throughout the 1920s and 1930s, they were involved in numerous Fleet Problems, which were large-scale training exercises that helped develop the doctrine later employed during the Pacific War. By 1941, the three ships were moved to the East Coast to join the Neutrality Patrols that protected American merchant ships from German U-boat attacks during the Battle of the Atlantic. Following the Japanese attack on Pearl Harbor in December, they were quickly transferred back to the Pacific, though they spent most of 1942 escorting convoys off the west coast of the United States. Beginning in mid-1943, they supported amphibious operations during the Aleutian Islands, Gilbert and Marshall Islands, and the Mariana and Palau Islands Campaigns. The Philippines Campaign followed in late 1944, though "Mississippi" was the only member of the class to participate in the early stages of the campaign, the other vessels being under refit at the time. There, she was present for the Battle of Surigao Strait on 24 October, the last battleship engagement in history.