Washington, D.C October 5, 1943

On this date in 1943 the Japanese news agency Domei acknow­ledged that the 7,903‑ton Kon­ron Maru was sunk by an Ameri­can sub­marine off the west coast of the Japa­nese home island of Honshū, with the loss of 544 lives. The troop­ship was sunk by the USS Wahoo using the new, still not per­fected Mark 18 elec­tri­cally pro­pelled tor­pedo based on a German design, the G7e, several of which had been retrieved by the Allies after running ashore. The Wahoo, skippered by the legen­dary Dudley “Mush” Mor­ton, was one of the most cele­brated sub­ma­rines of World War II, sinking 27 ships, totaling 119,100 tons, and damaging two more, for an additional 24,900 tons, in six patrols, more than any other sub­ma­rine of the time. On this, her seventh and last patrol, the Wahoo was credited by the Japa­nese with sinking four more ships (this included the previously men­tioned Kon­ron Maru), for 15,144 tons using Mark 18 tor­pe­does before enemy anti­sub­ma­rine forces sank her in the La Perouse (Soya) Strait between Russia’s Sakhalin Island and the northern Japanese island of Hok­kaidō on October 11, 1943, with a loss of all hands (80 men).

One advantage of the Mark 18 was that it could be fired in shal­lower waters than older steam tor­pe­does like the Mark 14. It was 20‑1/2 ft long and 21 inches in dia­meter, weighing in at a little over 3,000 lb. It had a war­head of 600 lb of Tor­pex (50 per­cent more power­ful than TNT by mass) with a con­tact explo­der. Owing to its 90 hp direct-current elec­tric motor it had a rela­tively slow speed of 29 knots (33 mph) compared to the Mark 14’s 45 knots and a maximum range of 4,000 yards.

Another advantage the Mark 18 had was this: Because of its electric pro­pul­sion system, the torpedo left no wake of bubbles or turbine exhaust like its older cousin, the Mark 14, did—an im­por­tant virtue in day­time engage­ments. Unfor­tu­nately the Mark 18 shared the same defect that its cousin did: it had no pro­tec­tion against cir­cu­lar runs. A cir­cu­lar run by a Mark 18 claimed the USS Tang for cer­tain and pos­si­bly other U.S. sub­ma­rines. (Tang’s nine sur­vi­vors, including its skip­per and former Wahoo execu­tive officer Richard O’Kane, were picked up the next morn­ing by a Japa­nese destroyer and in­terned until the end of the war.) By July 1944, an im­proved Mark 18 appeared. Some 30 per­cent of torpe­does fired by U.S. submarines in the Pacific War were Mark 18s.

USS Wahoo, 1941–1943

USS "Wahoo" off Mare Island Navy Yard, California, July 1943USS "Wahoo" sinks Japanese freighter

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. Recog­nized as a “One-Boat Wolf Pack,” the Wahoo received the coveted Presidential Unit Citation for her third patrol.

Right: The Japanese freighter Nittsu Maru sinks after being tor­pe­doed by the USS Wahoo on March 21, 1943. Within six hours of the surprise Japa­nese attack on the U.S. Pacific Fleet anchored at Pearl Harbor, Hawaii, the U.S. Navy adopted a policy of unre­stricted sub­ma­rine war­fare against Japan. Amer­i­can sub­ma­rines attacked with­out warning war­ships, trans­port ships, com­mer­cial ves­sels, and civil­ian pas­sen­ger ships flying the Japa­nese flag. 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. A tragic conse­quence of this “sink ’em all” cam­paign is that more than 20,000 Allied POWs trans­ported in Japa­nese “hell ships,” as they were known, died when the ships were attacked by Allied sub­marines (at least 8 different U.S. submarines) and aircraft. (See Gregory F. Michno, Death on the Hellships: Prisoners at Sea in the Pacific War.)

USS "Wahoo" with broom and pennant, Pearl Harbor, 1943Morton (left) and O’Kane on "Wahoo" bridge, February 1943

Left: Affixed to the Wahoo’s peri­scope is a broom (top center in photograph), which the sub proudly displaced on its return to Pearl Harbor on Febru­ary 7, 1943. The broom indicated that the oceans had been “swept clean” of the enemy. The pen­nant flying from the snorkel reads, “Shoot the sunza bitches.” The Wahoo was lost in October of the same year to a Japa­nese aerial depth-charge striking near the con­ning tower as she passed from the Sea of Japan west through the La Perouse Strait to the Sea of Okhotsk. The wreck was found intact on July 28, 2006, by a team of Russian divers at a depth of 213 ft.

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. O’Kane would later assume command of the USS Tang. Despite the odds—one in five sub­marines like the Wahoo and the Tang were lost to enemy action, the U.S. Navy’s under­water war­riors accounted for 60 per­cent of Japa­nese shipping losses, and were a major factor in winning the Pacific War.

Submarine Warriors Dudley “Mush” Morton and Richard O’Kane of the USS Wahoo