With World War II raging in Europe and German U-boats raiding shipping in the western Atlantic Ocean and the Caribbean, S-boats like S-30 were assigned to Submarines, Patrol Force (known as Submarines, Atlantic Fleet after February 1941) and conducted training and the development of tactical skills. From New London, she operated along the mid-Atlantic and northeastern coasts of the United States into the spring of 1941. She then served briefly in the Bermuda area before returning to New London. In early July 1941, S-30 proceeded to Philadelphia, Pennsylvania, for overhaul. In September 1941, she emerged from the shipyard, returned to New England, and resumed submarine and antisubmarine warfare training operations in the Long Island Sound, Narragansett Bay, Casco Bay, and Placentia Bay areas. World War II First, second, and third (defensive) war patrols The United States entered World War II on 7 December 1941 with the Japanese attack on Pearl Harbor, and S-30′s division, Submarine Division 52, soon was reassigned to the Panama Canal Zone for defensive patrol dutues. Departing New London on 31 January 1942, she hunted for enemy submarines along her route which took her via Bermuda and Mona Passage into the Caribbean Sea. On 16 February 1942, she arrived at Coco Solo, Panama, from which she conducted two more defensive patrols in the western approaches to the Panama Canal, from 10 to 31 March 1942 and from 14 April to 13 May 1942, before she was ordered to California to prepare for service in the Aleutian Islands. She underwent repairs at San Diego, California, then, inmid-July 1942, she started for the Territory of Alaska. While en route, engine trouble forced her into Mare Island for repairs, but on 1 August 1942 she resumed her northward voyage. Fourth (first offensive) war patrol On 12 August 1942, S-30 departed the submarine base at Dutch Harbor on Amaknak Island off Unalaska in the Aleutians to begin her fourth — and first offensive — war patrol. Moving through fog, she arrived off Attu Island — occupied by the Japanese at the beginning of the Aleutian Islands campaign in June 1942 — in the western Aleutians on 16 August 1942, her crew sighting only the hazy outline of Cape Wrangell through the fog. She continued on to patrol across the anticipated Japanese shipping lanes between Attu and the northern Kuril Islands. On the afternoon of 7 September 1942, three Imperial Japanese Navy