USS Thresher (SS-200) - Thirteenth Patrol

Thirteenth Patrol

On 14 June 1944, Thresher headed out for her 13th war patrol. 25 June, she joined a "wolfpack" that also included Apogon (SS-308), Guardfish (SS-217), and Piranha (SS-389). Nicknamed the "Mickey Finns" and under the overall command of Captain William V. "Mickey" O'Regan (flying his flag in Guardfish), the group picked up "ditching signals" from a downed aircraft that afternoon and changed course to investigate. Arriving in the vicinity on 27 June, they found only a drop tank and no trace of plane or pilot.

Over the succeeding days, the boats observed several planes but contacted only a few fishing vessels and small patrol craft. This drought of targets continued until 11 July, when Thresher made radar contact with a group of six ships steaming on the Formosa-Luzon route. As she changed course to intercept, she dispatched contact reports to the other boats. Guardfish and Apogon picked up the contact, but Piranha could not. Thresher deployed to a position 15,000 yards (14,000 m) astern of the convoy, to trail the enemy group and be ready to pick off stragglers. Guardfish took the enemy's port flank, and Apogon maneuvered to the convoy's starboard quarter.

A Japanese escort latched on to Thresher, however, and trailed her, depriving her of a chance to attack the convoy. Meanwhile, Piranha managed to sink a 6,504-ton passenger/cargo ship. Apogon was rammed and forced to return to base for repairs.

Rendezvousing on 13 July, the remaining boats resumed the hunt. At 16:00 on 16 July, Thresher sighted smoke on the horizon. She surfaced and dispatched a contact report. After a cat-and-mouse period of some two hours, she noted the convoy consisted of six ships: a large tanker, three freighters, and two escorts.

Thresher closed beneath a clear and dark night sky. At 23:29, with the range to the near escort at 2,000 yards (1,800 m), she commenced fire. Three torpedoes sped from the forward tubes toward the lead escort, three to the first freighter. Thresher then turned and emptied all four stern tubes at the second freighter. Four explosions were sighted and as Thresher departed at high speed, another six soon after.

Commencing a reload of her tubes at midnight (00.00 or 24.00), Thresher returned to the area and continued the attack on the convoy which consisted now of only three ships: a freighter, the oiler, and an escort. At 01:18, Thresher fired two bow tubes at the escort and three at the leading freighter; the sub then fired her stern tubes at the oiler. Soon thereafter, Thresher heard at least six explosions. The escort promptly began a depth charge barrage. Returning to periscope depth, Thresher found the convoy had remained stubbornly afloat. She began reloading her tubes again at 01.22 and returned to the chase.

While tube number six was still being reloaded, Thresher fired two other bow tubes at the freighter, two more at the oiler, and the remaining full one at the escort; she then swung about and fired one stern tube at the latter. Two torpedoes exploded at 02:46, and the cargo ship sank immediately. One minute later, two "fish" struck the oiler. A tremendous explosion lighted the entire sky, and the ship sank within 15 seconds.

While it could not be ascertained whether or not the last escort went down, the effect of two torpedo hits made it likely he had been heavily damaged. All torpedoes expended, Thresher headed for Midway. The boat claimed to have destroyed the entire convoy, but a port-war assessment confirmed only two cargo vessels, Sainei Maru (4,916 tons) and Shozan Maru (2,838 tons), and no escort. Thresher did, however, receive the Navy Unit Commendation for the patrol.