USS Threadfin (SS-410) - Third War Patrol

Third War Patrol

At Pearl Harbor, she underwent refit followed by a brief four-day training period before departing on her third and final war patrol. She stopped briefly at Guam for voyage repairs; then continued on to her assigned area in the Yellow Sea and the East China Sea. She closed her first victim, a three-masted schooner, to inspect her and determine her nationality. Finding her to be enemy-operated and worthy of attack, the submarine opened up with her five-inch (127 mm) deck gun. Fifteen hits later, the schooner vanished beneath the waves. Threadfin rescued nine crewmen from the schooner and learned that her victim had been bound for Dairen laden with coal. The next day, the submarine encountered a freighter sunk in shallow water and surrounded by small boats, apparently conducting some variety of salvage operations. She fired a single torpedo which caused the wreck to settle a further ten feet and which she hoped would suspend the suspected salvage operations. Closer inspection, however, indicated that the boats were fishing, not conducting salvage operations.

Soon thereafter, Threadfin sighted a four-masted cargo schooner and sank her in a gun attack. The following afternoon, her deck gun accounted for another cargo schooner. On the 19th, she stopped a group of five two-masted cargo junks for inspection but allowed them to continue their voyage after identifying them as friendly Chinese. The next night, she made a surface radar torpedo attack on an enemy ship shrouded by heavy fog. She loosed a spread of five torpedoes, of which two found their mark. The target sank within five minutes without ever being visually sighted from Threadfin.

The submarine concluded her offensive operations near the Strait of Tsushima. After a day of submerged patrolling without sighting a worthwhile target, she received word that night that submarine Sea Robin (SS-407) had come upon a patrol craft heading north and four small cargomen heading south. While Sea Robin took on the patrol craft, Threadfin hit the small convoy. During the ensuing night gun action, she sank two of the four tiny merchantmen and forced the other two into Sea Robin’s path. The two American submarines dispatched all four. On the return trip from her final war patrol, Threadfin rescued three survivors from a downed American flying boat and took them to Guam where she arrived on 27 July.