A new submarine on her first war patrol, this was the Japanese submarine I-42. She commissioned at Yokosuka and after training and trials she set off on Feb. 12, 1944 for operations near Truk. Finding no targets the boat touched at Saipan and then moved on to Truk. Her next mission was to resupply troops at Palau, after loading supplies and a number of personnel she left Truk on Mar. 15, 1944.

The U.S. Navy knew of her destination due to the Ultra decrypts and directed USS Tunny SS-282 to intercept the I-42. Tunny was on her fifth war patrol having departed Pearl Harbor on Feb. 27, she touched at Midway on Mar. 2nd and continued on to her patrol area off the Palau islands in the Caroline Islands.

The day before I-42 was sunk, Tunny attacked a Japanese convoy sinking the 6.500 ton tanker Iro, but she and her crew paid for sinking the tanker when the Japanese loosed over 85 depth charges against the Tunny. The prolonged attack surely rattled the crew, but did little damage to the boat.

Lt. Commander John A. Scott and his Tunny waited in the waters off Angaur Island, Palau for the I-42, at 21:19 hours he picked the boat up on radar about 13,000 yards away. As Scott moved toward the I-42 the lookout on the Japanese submarine sighted Tunny, it was now a game of cat and mouse, both boats trying to get into position to kill the enemy, Scott and the Tunny against Commander Tsunayoshi Ogawa and the I-42.

The maneuvers of the two boats lasted ninety minuets, but it was Tunny who was the victor, Scott fired four torpedoes at the I-42 and two found the mark. Scott dove the Tunny to avoid a collision and while under the soundman could hear the death throes of the I-42, her screws stopped and crackling sounds lasting almost an hour were the last sounds ever heard from I-42 and the 102 people on board.

Scott and his crew almost bagged another prize only a few days later, this time the target was one of the largest battleships ever built, Musashi. The Japanese were evacuating Palau before an expected American bombing raid and Musashi and a destroyer screen had just pulled out when Tunny fired six torpedoes at the ship. They were sighted by the destroyers and Musashi was signaled, but one (Tunny claims two) hit the Musashi in the port bow. The destroyers Urakaze and Isokaze drop thirty-seven depth charges on the unwanted visitor, but Tunny and her crew survive. Musashi was repaired and sailed that evening for Kure.

All six of the sister ships to I-42 were lost during the war, and all were lost with all hands on board.