U.S. Seventh Fleet HQ · July 30, 1943

During the Pacific War U.S. submarines fired some 11,000 torpe­does, sinking hun­dreds of Japa­nese war­ships and well over one thous­and mer­chant ships. The num­ber of lives lost in the latter engage­ments is esti­mated at 116,000 Japa­nese mer­chant sea­men, with 70,000 casu­al­ties the result of U.S. submarine actions.

In mid-March 1942 the USS Pollack made the first sub­marine attack on a war patrol using its three‑inch deck gun and a .50 caliber machine gun. The objects of the sur­face attack were two Japa­nese sam­pans, pre­sum­ably civil­ian craft and unarmed. During 1942 U.S. sub­marines reported 34 attacks on sam­pans, trawlers, and a schooner. The num­ber of attacks increased to 80 in 1943, the year that U.S. Seventh Fleet Bul­le­tin No. 15, issued on this date, approved sub­marine deck gun attacks against “Chin­ese” junks, schooners, and other small ves­sels. Their sinking over the long haul would produce impressive results, the bulletin prophesied.

With mounting ship­ping losses to their large cargo ships—less than 1 mil­lion tons lost at the end of 1942, 1.77 mil­lion tons at the end of 1943, and 2.5 million tons through 1944—the Japa­nese in­creas­ingly resorted to smaller craft to trans­port person­nel, fuel, food, raw and finished mate­rials, and mili­tary equip­ment between their Home Islands and their south­ern resource areas and island gar­ri­sons. Small craft were also engaged in trans­porting goods along the coasts of their Home Islands due to the coun­try’s under­developed railway system and rudimentary roads.

From 1944 to 1945, with fewer and fewer large Japa­nese ships in the region, the num­ber of deck gun attacks by U.S., British, and Dutch sub­marines on smaller craft doubled, from 508 to 1,044, with more than half being Amer­i­can kills. By war’s end most large Japa­nese fishing vessels, junks, schooners, traw­lers, and coasters in South­east Asia had been destroyed in the con­text of “total war” against the Japanese Empire.

Through­out the Pacific War the issue of whether to attack and sink defense­less or lightly armed small craft using deck guns remained a per­sis­tent moral and tacti­cal dilem­ma for Allied skippers and sea­men—because doing so meant killing crews (often made up of multi­ple Asian nationalities and often with their families) close up and face-to-face.

Sinking Enemy Ships in the Pacific, 1941–1945

USS "Wahoo" sinks Japanese freighter "Nittsu Maru," March 21, 1943USS "Nautilus" sinks Japanese destroyer "Yamakaze," June 25, 1942

Left: The Japanese freighter Nittsu Maru sinks after being tor­pedoed by the USS Wahoo on March 21, 1943. Within six hours of the Japanese surprise attack on Pearl Harbor, Hawaii, the U.S. Navy adopted a policy of unre­stricted sub­marine war­fare against Japan. Amer­i­can sub­marines attacked war­ships, com­mer­cial ves­sels, and civil­ian pas­sen­ger ships flying the Japa­nese flag without warning. From 1943 Allied subs waged an increas­ingly effec­tive cam­paign against ill-pro­tected Japa­nese mer­chant shipping and the Japa­nese Navy. By the end of the war in August 1945 the Japa­nese mer­chant marine had less than a quarter of the ton­nage it had in Decem­ber 1941, when it already had a deficit of 40 per­cent in ship bottoms flying flags of Japan’s new enemies.

Right: Torpedoed Japanese destroyer Yamakaze photo­graphed through the peri­scope of the USS Nautilus on June 25, 1942. It is notor­i­ously dif­fi­cult to pro­vide a defini­tive accounting of sur­face ves­sel losses over the course of the war. The best esti­mate is that U.S. sub­marines sank roughly 200 Japa­nese wars­hips and close to 1,300 Japa­nese mer­chant ships, for a loss of 52 U.S. sub­marines. (One in five U.S. sub­ma­riners was lost during the war, the highest casu­alty per­centage of any ser­vice.) Japa­nese losses due to all sinking agents (e.g., sub­marines, mines, air­craft, and shore bat­teries) of what­ever Allied nation appear to number 2,117 mer­chant ships, 611 naval ships, and 15,518 civilian ships (small craft).

USS "Wahoo" off Mare Island Navy Yard, California, July 1943Morton (left) and O’Kane aboard "Wahoo," February 1943

Left: The USS Wahoo off Mare Island Navy Yard, Cali­for­nia, 1943. Its skipper was Lt. Cmdr. Dudley W. “Mush” Mor­ton (1907–1943), the first super­star of the U.S. sub­marine ser­vice. He and his crew were respon­si­ble for sinking at least 19 Japa­nese ships on six patrols, more than any other sub­marine of the time. His motto, em­bla­zoned on the sub’s pen­nant, was “Shoot the Sunza Bitches.” The Wahoo, recog­nized as a “One-Boat Wolf Pack,” received the coveted Presidential Unit Citation.

Right: Morton (left) speaks with his execu­tive offi­cer, Richard O’Kane, on the bridge of the Wahoo days after tor­pe­doing the Japa­nese troop trans­port Buyo Maru, north of New Guinea, on Janu­ary 26, 1943, on the sub’s third patrol. Sur­facing, the Wahoo used its four-inch deck gun, two 20mm guns, crew rifles, and pistols to fire on shipwreck sur­vi­vors, some floating in the ocean, some in roughly 20 life­boats. O’Kane claimed that the sur­vi­vors opened fire first and crew­men responded with every­thing they had for the next 20 minutes. Close to 300 sur­vi­vors of the sinking died before the Wahoo left the scene.

Crew of USS Wahoo: No Mercy on Shipwreck Enemy (Video Con­tains Disturbing Scenes of Crew­men Firing on Ship­wreck Sur­vivors, January 26, 1943)