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DEPARTMENT OF THE NAVY -- NAVAL HISTORICAL CENTER
805 KIDDER BREESE SE -- WASHINGTON NAVY YARD
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Thresher

 

A class of shark which is harmless to man and easily recognizable because its tail is longer than the combined length of body and head.

 

I

 

(SS-200: dp. 1,475 (surf), 2,370 (subm.); 1. 207'2"; b. 27'3'; s. 20 k. (surf.), 8.75 k. (subm.); cpl. 59; a. 10 21" tt., 1 S", 1 .30-cal. mg., 1 .50-cal. mg.; cl. Tambor)

 

The first Thresher (SS-200) was laid down on 27 April 1939 at Groton, Conn., by the Electric Boat Co.; launched on 27 March 1940; sponsored by Mrs. Claud Jones; and commissioned on 21 August 1940, Lt. Comdr. William L. Anderson in command.

 

Following training and sea trials, Thresher got underway from New London, Conn., on 25 October for engineering trials in Gravesend Bay, N.Y., and shakedown off the Dry Tortugas.

 

She operated along the east coast through the end of 1940 and into 1941. During a call at Annapolis, Md., Thresher hosted Rear Admiral Russell Willson as a guest on 31 April before she got underway the following day for the Caribbean. After emerging on the Pacific side of the Panama Canal on 9 May and stopping at San Diego from the 17th through the 21st, Thresher arrived at Pearl Harbor on 31 May. She operated out of the Hawaiian Islands into the fall of 1941, as tensions rose in the Far East and the United States prepared for war in both oceans.

 

Thresher and sister-ship Tautog (SS-198) departed the submarine base at Pearl Harbor on 31 October bound for a simulated war patrol north of Midway atoll. They both carried fully-armed torpedo warheads. Tautog returned first; and, on 7 December, Thresher neared the Hawaiian Islands to end her part of the cruise. Escorted by Litchfield (DD-336) through Hawaiian waters lest she be mistaken for a Japanese submarine, Thresher received word at 0810 that Pearl Harbor was under attack by Japanese aircraft.

 

Litchfield promptly set off to join American light forces departing from the harbor, leaving Thresher alone to conduct her first real war patrol. However, the destroyer was ordered back to escort the submarine; radio contact between the two ships was established; and a rendezvous arranged.

 

At the pre-appointed time, Thesher poked up her periscope to have a look, and noticed a destroyer— similar to Litchfield—approaching, bows-on. The submarine's commander and a signalman felt certain that the oncoming ship was Litchfield. Nevertheless, instead of a warm reception from friends, she got a hot reception from the destroyer's forward gunners, who opened fire on the submarine as soon as her black conning tower broke the surface.

 

Quickly reappraising the situation, Thresher immediately went deep to avoid the attentions of "friendly forces." She again tried to enter the harbor on the 8th, but was driven off by depth-bombs from a patrol plane, before Thornton (AVD-11) finally arrived to provide safe-conduct for the submarine at midday on the 8th.

 

Departing Pearl Harbor on 30 December, Thresher headed for the Marshalls and Marianas. Reconnoitering Majuro, Arno, and Mili atolls from 9 to 13 January 1942, the submarine shifted to waters off Japanese-held Guam in the early morning darkness of 4 February. A little before daybreak, she sighted a small freighter seven miles north of Agana Harbor and closed for the attack. She loosed a three-torpedo spread, holing the ship and sending her down by the bow and dead in the water. Thresher then fired another spread of torpedoes, but all mised due to the target angle. When the submarine returned to the scene one-half hour later, the once-wallowing freighter was no longer in sight; and Thresher felt that she had scored a "kill." Her claim, however, was not substantiated in postwar accounting.

 

For the next six days, Thresher reconnoitered the seas between Tinian and Rota in the Marianas, having departed the Guam area to evade possible Japanese antisubmarine measures. She found nothing there and set a course for home. While en route, an overzealous Navy plane attacked the ship on 24 February but, fortunately, did not damage the submarine which returned safely to Pearl Harbor on the 26th.

 

The newly refitted fleet boat then departed Pearl Harbor on 23 March for waters near the Japanese home islands. As a subsidiary mission on this patrol, Thresher was to gather meteorological data in the waters off Honshu and report it to Pearl Harbor. This information was needed by Vice Admiral Halsey's task force—centered around aircraft carriers Enterprise (CV-6) and Hornet (CV-8)—then approaching the Japanese home islands. Embarked in Hornet were 16 Army B-25 medium bombers, under the command of Lt. Col. James H. Doolittle, which would take off at sea and fly to Japan for strikes on Tokyo on 18 April. Conducting routine exercises and drills while en route, Thresher sighted a large Japanese freighter on the morning of 10 April. She closed for the attack and launched a three-torpedo spread. All three missed, and the freighter escaped in the mist. When the target emerged from the murk, her course precluded a further attack; and the frustrated submarine proceeded on her way.

 

She sighted a second target later that day, and her hunting was better this time around. One torpedo broke the back of the 3,000-ton freighter Sado Maru off Yokohama harbor, sending her beneath the waves in three minutes. Enemy antisubmarine craft picked up Thresher within 30 minutes of the sinking, and the submarine began a game of hide-and-seek. During one depth-charge attack, the boat lost depth control and began plunging towards unexplored depths before her bow was trimmed, and she regained control.

 

On the 13th, while running on the surface to recharge her batteries, Thresher took a high wave over her conning tower. Water cascaded down the open conning tower hatch and rushed into the ship, grounding many electrical circuits. For a short time, there was a decided danger that chlorine gas would be released to endanger the crew, but quick thinking and damage control action prevented that development. Eventually, all short circuits were repaired; and the boat pumped out.

 

The next day, Thresher departed her assigned patrol area and turned her attention to gathering meteorological data. Thresher conducted periscope patrols in the advance screen of Halsey's task force, searching for any enemy craft that could warn the Japanese homeland. She was detached from this duty on the 16th and, after evading two Japanese patrol planes, returned home to Pearl Harbor on the 29th.

 

Commencing her fourth war patrol on 26 June, Thresher headed for waters between the Palaus and the Marshalls. She approached a tanker off Enijun Pass on 6 July and commenced an attack. One torpedo struck home near the stern, and Thresher felt a muffled explosion. Large amounts of smoke boiled into the sky from the stricken tanker's stern. Soon, Japanese aircraft arrived on the scene and assisted the two surface escorts during an ensuing three-hour depth bomb counterattack. The submarine then resumed her search for "targets of opportunity."

 

Midway between Kwajelein and Wotje atolls, Thresher sighted the 4,836-ton motor torpedo boat tender Shinsho Maru. Two torpedo hits caused tremendous explosions to shake the area, and Shinsho Maru sank beneath the waves. The submarine then withdrew to await expected Japanese countermeasures. Within the hour, two depth charges shook the ship, and 10 minutes later, a banging and clanking alerted Thresher to the fact that the Japanese were apparently bringing a large grapnel into play in an attempt to capture the submarine.

 

Thresher fought for her life. After applying full right rudder, she made a 10 minute, high-speed run which shook her free from the giant hook. Then, as a depth charge exploded near her conning tower, the boat went into deeper water. With a bending and twisting turn, the submarine left the enemy behind, with some 30-odd depth charges exploding in her wake. Shaken but not seriously damaged, Thresher made minor repairs as she headed for Truk to reconnoiter the passes leading into this enemy naval bastion.

 

Missing a freighter with torpedoes on the night of 20 July, Thresher surfaced in a rain squall before daybreak on the 21st. The boat's sonar picked up the sound of screws, close and closing. Soon an enemy patrol craft came into view, approaching on a collision course. Surprisingly, the Japanese chose not to ram, but instead put over his helm hard right, and came to a parallel course some 50 yards away. With the two antagonists perhaps mutually astonished to find each other in the area, Thresher "pulled the plug" to dive deep, while the enemy's guns fired close but ineffective salvoes into the water ahead of the disappearing submarine.

 

After escaping by silent-running to the Palaus, Thresher tangled with an enemy "Q"-ship off Ambon in the former Netherlands East Indies. The two torpedoes that she fired at the enemy failed to detonate, and the "Q"-ship subjected Thresher to an eight-charge barrage before giving up the attack. Since she had been reassigned to the Southwest Pacific Submarine Forces, Thresher sailed for Australian waters and terminated her fourth war patrol at Fremantle on 15 August.

 

Following refitting, Thresher loaded mines and departed Fremantle on 15 September, bound for the Gulf of Siam. She fired torpedoes at two freighters north of Lombok Strait on 19 September but was unable to determine the results of her attacks. On the night of the 25th, luck again failed to smile on the submarine as a single torpedo streaked beneath a large, high-speed target in the Sulu Sea.

 

Thresher later surfaced at 2300 and proceeded on a course which took her north to Pearl Bank. There, in the northernmost reaches of the Gulf of Siam, she made one of the first mine plants by a submarine in the Pacific war. These strategic "plants" by Thresher and her sisters, in subsequent patrols, covered Japanese shipping lanes in areas in the southwest Pacific command previously unpatrolled by submarines. Later, these minefields filled the gap between patrol zones along the coastal waters of Malaya, Siam, and Indochina, when many submarines were diverted to participate in the Solomons campaign.

 

While reconnoitering off Balikpapan, Borneo, and the Celebes coast, Thresher sighted a tanker aground on a reef off Kapoposang Island in the Java Sea. Thresher soon surfaced for a deck-gun attack and left the enemy ship with decks awash. The submarine then returned to her base at Fremantle on 12 November for refit.

 

Underway from Fremantle on 16 December, she arrived off Soerabaya, Java, on Christmas Day. She intercepted a convoy of freighters, escorted by two destroyers, several subchasers, and two aircraft. Slipping past the escorts, Thresher sent five torpedoes towards the leading three ships. Two successive explosions followed. Rising to periscope depth, the submarine observed the second ship in the column down by the bow, with her stern up in the air and her screws, still revolving, out of the water. A second ship lay dead in the water, enveloped in smoke. Escaping unscathed from this tangle with a coastal convoy, Thresher sighted an enemy aircraft carrier the next night, but was picked up by escorts and held at bay for more than an hour while the tempting task force faded into the night.

 

On the night of 29 December, Thresher made contact with the 3,000-ton freighter Haichan Maru. Just before midnight, she fired a spread of torpedoes at the cargo-man; but all missed or ran too deep. Undaunted, Thresher waited for the moonrise and then surfaced to utilize her deck gun. Outmaneuvering the enemy, who tried to ram her, Thresher scored eight hits in succession amidships with her 5-inch main battery, stopping Haichen Maru dead in the water. A single torpedo finished the deck gun's work, and the enemy vessel slipped beneath the waves stern first in the predawn darkness of 30 December 1942.

 

Returning to Fremantle on 10 January 1943, the submarine got underway 15 days later for her seventh war patrol. At 1100 on 14 February, Thresher made contact with a Japanese 7-65-class submarine to the east of Thwartway Island. She launched two torpedoes; but one turned out to be a dud, and the other exploded harmlessly on the ocean bottom. Turning north and firing deck guns, Thresher's adversary soon disappeared from sight over the horizon.

 

Three days later, Thresher reconnoitered Flying Fish Cove, off Christmas Island, and photographed docks, houses, phosphate loading areas, and gun emplacements. Then, after proceeding to the Flores Sea, she intercepted a three-ship convoy escorted by two antisubmarine vessels on 21 February. Loosing a two-torpedo salvo, Thresher scored a hit with one on the stern of transport Kuwayama Maru. Thresher then evaded 13 depth charges before returning to periscope depth a little more than an hour later. She observed her target lying dead in the water while barges carried troops from the first transport to an undamaged sister. As escorts searched the waters nearby, Thresher closed and torpedoed the second transport as it was lying-to during the transfer of survivors from the first. Two loud explosions reverberated in the background as the submarine dived to avoid possible countermeasures.

 

The following day, Thresher returned to celebrate Washington's Birthday by finishing off Kuwayama Maru. The enemy ship, by then abandoned, jack-knifed into a "V" shape and sank within three minutes.

 

Thresher prowled for more game and came upon a tanker and a freighter on 2 March. A single torpedo hit on the 5,232-ton tanker Toen Maru sank the ship. The freighter, sighting the torpedo wakes, took evasive action to avoid being hit. Then, a nearby escort arrived on the scene and kept Thresher at bay while the second target escaped. The submarine subsequently concluded this patrol with her arrival at Fremantle on 10 March.

 

Her eighth war patrol (from 4 April to 23 May) was uneventful, but her ninth saw the submarine score another "kill." Off Balikpapan, Borneo, she sighted a three-ship convoy, escorted by a sole destroyer on the night of 30 June. After an unrewarding try with a trio of torpedoes, Thresher dodged the escort's depth charging attack and returned with the scent of a kill. Tracking with radar, Thresher set a tanker ablaze from stem to stern and scored hits on the 5,274-ton passenger-freighter Yoneyama Maru, which sent the hapless merchantman to the bottom of Makassar Strait.

 

Later, while heading for Tambu Bay on the morning of 5 July, Thresher tracked a tanker. Chasing her quarry along the Celebes coast, the submarine lurked nearby until the escort left the tanker. Thresher then closed, loosed three torpedoes, and scored one hit on the bow of the enemy vessel. However, this blow failed to stop the tanker, which fired her guns to keep Thresher at bay as she escaped at high speed.

 

Four days later, Thesher arrived off Catmon Point, Negros Island. Under cover of darkness, the submarine surfaced and delivered 500 nounds of stores and 40,000 rounds of ammunition to Filipino commandoes. In addition, the crew of the submarine contributed their personal rations of cigarettes, matches, soap, candy, and other personal gear to those brave men who were resisting Japanese occupation. Receiving intelligence documents in return, Thresher got underway for a resumption of her war patrol shortly before midnight on 9 July. Thresher soon departed the Philippines and sailed via Pearl Harbor and Midway to the west coast for a major overhaul at the Mare Island Navy Yard, Vallejo, Calif.

 

Newly refitted, Thresher departed the west coast on 8 October and arrived at Pearl Harbor one week later. She commenced her tenth war patrol as she departed the Hawaiian Islands on 1 November, bound for the waters north of the Carolines. Prowling north of Truk, Thresher commenced tracking a five-ship convoy on the morning of 12 November and slipped past two escorts shortly before midnight.

 

She fired a spread of three "fish" into Muko Maru, a 4,862-ton transport. Then, an attack on another Maru failed, as a second trio of torpedoes missed their mark. Escorting antisubmarine craft hunted in vain for the American attacker, dropping 20 depth charges in a harassing barrage.

 

Thresher's, 11th war patrol took her to the South China Sea below Formosa. While cruising on the surface on 10 January 1944, Thresher sighted a pair of masts, low on the horizon, and quickly dove to avoid possible detection. Coming to periscope depth soon thereafter, she approached cautiously, keeping in mind that the ship may have been the advance screen of a convoy. The contact proved to be a 150-ton trawler. Thresher battle-surfaced, and her gun crews tumbled out on deck to man the guns. Opening the action from 6,000 yards, the submarine expended 45 5-inch shells; 1,000 rounds of .50-caliber machinegun fire; and 770 20-millimeter shells. Finally, the trawler went down. The submarine's war patrol report noted the tonic effect on the submersible's crew: "Not much damage was done to the Imperial war effort," the commanding officer, Comdr. Duncan C. MacMillan, commented, "but the action had a good psychological effect on the crew."

 

Thresher next set course for the Luzon Strait, between Batan Island and Luzon, in the Philippines. At 1143 on the 15th, Thresher came to the surface, only to spot a Japanese aircraft carrier and an escorting destroyer soon thereafter. The submarine "pulled the plug" and submerged but soon came up to periscope depth to observe the enemy destroyer rapidly approaching. With insufficient time to maneuver for a "down the throat" shot, Thresher went deep and rigged for silent running. The destroyer churned overhead and dropped four depth charges—none of which fell very close to the submarine. After remaining above the submarine for two hours, the escort finally turned away, leaving Thresher unscathed.

 

Again coming to periscope depth at 1700, Thresher soon sighted a four-ship convoy escorted by a sole subchaser at a range of 12,000 yards. Surfacing at 1911, Thresher began the chase, tracking the convoy by radar. The three leading targets steamed in column formation, roughly 500 to 800 yards apart, with the fourth some 6,000 yards astern. The escort was between the third and fourth merchantmen. Approaching from the westward, to take advantage of the moonrise, the submarine stalked her prey, whose behavior had been, to a point, predictable.

 

Previously zigzagging every 10 minutes, the convoy changed course at 2155—giving Thresher an excellent setup for her stern tubes. At 2207, the submarine let fly with four torpedoes from 1,800 yards at the lead ship, the 6,960-ton freighter Tatsuno Maru. Thresher observed two hits; and the vessel, with her bow in the air, was observed in a sinking condition.

 

Thresher next fired three bow tubes at the second target—later identified as 4,092-ton freighter Toko Maru. Three torpedoes struck the ship—evidently a tanker—and literally blew her to pieces. The cargo of oil burst into flames and illuminated the night as brightly as day.

 

The third ship commenced fire with deck guns on Thresher, passing down the port side at 800 yards away. With the submarine now illuminated by the burning oil, and with her after tubes spent, Thresher's historian noted later "that our usefulness for the moment was over." Accordingly, Thresher dove as bullets from the approaching escort splashed nearby.

 

Thresher counted some 20 explosions from depth charges before the patrol craft left an hour later. When she surfaced, Thresher observed that she was again all alone and then commenced patrolling along the Singa-pore-to-Japanese Empire trade route.

 

On 26 January, however, Thresher made radar contact with a small convoy. Closing her sighting, the submarine soon spotted two ships steaming along beneath the overcast night skies. At 0011, Thresher fired three torpedoes from her bow tubes at the 1,266-ton freighter Kikuzuki Maru, before the submarine bent on full-speed ahead and hard right rudder to clear the area. Her "fish" scored a bullseye, and the quarry disappeared within a minute.

 

A second spread of torpedoes, fired 35 seconds after the first, plowed into 2,205-ton Kosei Maru, which sank soon thereafter. A fourth target made off to the south at high speed, "spraying the ocean with 5-inch ammunition." Resuming the approach at 0020, Thresher doggedly tailed the Japanese freighter for four hours before reaching a favorable attack position. Firing her last torpedoes at 0446, Thresher began to build up speed and had just commenced a turn when one torpedo struck the enemy ship, causing a tremendous explosion.

 

The blast slowed the freighter, but its tremendous concussion stopped the submarine dead in the water. All four main engines overspeed trips were actuated; cork insulation flew; lights broke; clocks stopped; and water poured down the antenna trunk. By the time Thresher regained battle readiness, the enemy was too far away to encourage further pursuit.

 

Well within the range of shore-based aircraft, Thresher quit the chase. Escorts, alerted to the fact that an American submarine was prowling in the vicinity, arrived on the scene and conducted a three-hour long, but futile, depth-charging. On the 28th and 29th, Thresher patrolled the Formosa-to-Palau shipping route, in the area of the Luzon Strait, before returning via Midway to Pearl Harbor where she arrived on 18 February. There, Lt. Comdr. MacMillan was awarded the Navy Cross for his aggressive action during the patrol.

 

Thresher went to sea on 18 March, departing Pearl Harbor for the central Carolines. She remained on air-sea rescue station during American carrier strikes on Truk, bombarded Oroluk Atoll on 11 April, and photographed islands in that group. The submarine played "hide and seek" with numerous enemy aircraft and witnessed several American bombing raids on Truk. She sighted only two enemy ships and was unable to attack either, before she returned to Pearl Harbor on 8 May.

 

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

 

Over the succeeding days, the submarines 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, the submarine dispatched contact reports to the other ships. Guardfish and Apogon picked up the contact, but Piranha could not. Thresher deployed to a position 15,000 yards astern of the convoy, to trail the enemy group and be ready to pick off stragglers. Guardfish took the enemy's port flank. Apogon maneuvered to the convoy's starboard quarter.

 

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

 

Rendezvousing on the 13th, the remaining submarines resumed their hunting. At 1600 on the 16th, Thresher sighted smoke on the horizon. She surfaced and dispatched a contact report. After a cat-and-mouse period of some two hours, Thresher noted that the convoy consisted of six ships: a large tanker, three freighters, and two escorts.

 

Thresher closed her prey beneath a clear and dark night sky. At 2329, with the range to the near escort at 2,000 yards, she opened fire. Three torpedoes sped from the forward tubes at the lead escort; three at the first freighter. Comdr. MacMillan then turned Thresher 150 degrees to port and launched four torpedoes at the second freighter. The submarine sighted four explosions and heard six soon thereafter, as she departed at high speed.

 

Commencing her reload at midnight, Thresher returned to the area and continued the attack on the convoy which had been pared down to three ships: a freighter, the oiler, and an escort. At 0118, the submarine fired two bow tubes at the escort and three at the leading freighter. She then swung 165 degrees to starboard to fire stern shots at the oiler. Soon thereafter, she heard at least six explosions. The escort promptly began a depth charge barrage. When Thresher returned to periscope depth, she found that the convoy had remained stubbornly afloat. Commencing another reload at 0122, the submarine continued to stalk her crippled prey.

 

Although still reloading tube number six, Thresher fired two bow tubes at the freighter; two at the oiler; and one at the escort. Then, Thresher swung about and fired one stern tube at the latter. Two torpedoes exploded at 0246, 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 actually went down, the effect of two torpedo hits made it likely that she had been heavily damaged. All torpedoes expended, Thresher headed for Midway. The submarine claimed to have destroyed the entire convoy, but a post-war assessment only credited her with two cargo vessels: the 4,916-ton Sainei Maru and the 2,838-ton Shozan Maru.

 

Thresher did, however, receive the Navy Unit Commendation and the citation noted the "outstanding heroism . . . persistent and daring coverage of Japanese-controlled waters . . . striking fiercely at the enemy in a brilliantly-executed attack on the night of 16 and 17 July 1944."

 

Upon completion of voyage repairs, Thresher stood out of Midway on 23 August, bound for her 14th war patrol which would take her to the Yellow and East China Seas. Six days later, while cruising on the surface, Thresher was battered by heavy seas which caused the ship to roll some 53 degrees from the vertical and produced waves up to 50 feet high.

 

Thresher arrived off the Japanese home islands on 3 September and made intermittent sweeps with her radar. Rounding the southern tip of Kyushu, the submarine sighted several small craft before making contact with a minelayer and two subchasers on the 10th.

 

Clearing the vicinity at high speed, Thresher headed for new patrol grounds.

 

The submarine was twice frustrated on the 13th, when a large oiler passed far out of reach and a freighter—attacked with four torpedoes—remained stubbornly afloat. An escorting aircraft harried the submarine and prevented her from attempting further attacks.

 

At 1531 on 18 September, Thresher sighted the masts, funnel, and bridge of a ship on the horizon. After determining the enemy's base course and zigzag plan, Thresher surfaced and locked the freighter onto radar contact at 1923. Another pip, an escort vessel, soon appeared on the radar screen.

 

By 2100, Thresher had maneuvered into position off the enemy's port bow and waited for the Japanese ships to make a zig which would place the submarine at a desirable point for the attack. Thresher closed in for the kill and loosed four torpedoes as the group turned to the right. The quarry, however, elected to move contrary to the hunter's expectations; and the first spread ran wide of its targets. Thresher, still undetected, quickly came about and fired four stern "fish" from 1,200 yards.

 

The second spread ran true and struck the 6,854-ton freighter Gyoku Maru. The explosions broke the cargo-man's back, and she quickly slipped from sight. Thresher retired at high speed when she detected the presence of three additional ships—including light cruiser Yubari—rapidly closing.

 

Reloading, Thresher turned upon her pursuers, loosing a spread of torpedoes which barely missed. Subsequently evading her hunters and shifting to waters off Manchuria, the submarine sighted only fishing craft until the 26th, when a large cargo vessel hove into sight at 0944. Thresher surfaced at 1315 and headed for the nearest point on the enemy's zigzag course. One hour later, the submarine spotted a floatplane on patrol, and hurriedly "pulled the plug" to submerge. As she went deep, one depth charge exploded nearby.

 

Staying under until 1600, Thresher came to the surface and picked up her target at 1815. The submarine then tracked her quarry until after sunset. Thresher's commander postulated that the enemy vessel was bound for Daisei Gunto and accordingly plotted course to intercept the enemy vessel before she could reach that destination, some three hours later.

 

Attacking from the bright moon side, Thresher fired two bow tubes—aiming one torpedo at the hull near the mainmast and one at the fore. Both struck home, and the 1,468-ton freighter Nissei Maru broke up and sank within one minute.

 

The following day—26 September—Thresher came upon a 5,000-ton oiler and cut loose with four stern tubes from a range of 4,000 yards. On Thresher's bridge, observers saw the enemy vessel, Koetsu Maru, disappear within a minute. Having now expended all of her torpedoes, Thresher headed for Midway. En route, on 3 October, the submarine sighted, tracked, and approached a small trawler. After sunset, Thresher surfaced and manned her deck guns. After firing 27 rounds of 5-inch ammunition, the submarine soon received an answer in the form of shells which fell around the submarine and forced her to back off. When it became too dark to see the target, Thresher left the trawler alone and resumed her passage to Midway.

 

After fueling at Midway on 8 October, Thresher sailed for the Hawaiian Islands and arrived at Pearl Harbor on the 12th. Following a lengthy refit, Thresher got underway on 31 January 1945 and proceeded to the Marianas in company with Tilefish (SS-307), Shad (SS-235), and Peto (SS-265). Eemaining at Saipan overnight, 12 and 13 February, the "wolf pack" pushed on toward its assigned patrol areas north of Luzon in the Philippines. However, Thresher's 15th war patrol proved to be largely unproductive. Only two of her contacts developed into torpedo attacks. One failed due to the target's shallow draft; and, in the second, the quarry shook off the hunter with evasive maneuvers. Thresher did, however, conduct air-sea guard patrols, standing ready to rescue ditched airmen; and conducted a shore bombardment of Basco Harbor, Batan Island, on 28 March. The latter part of this patrol was conducted in company with Piranha and Puffer (SS-268).

 

Clearing her patrol station soon thereafter, Thresher nested alongside Fulton (AS-11) for voyage repairs before pushing on for Oahu on 4 April. Arriving at Pearl Harbor 20 days later, Thresher thus ended her active combat service upon conclusion of her 15th war patrol. Undergoing a routine refit and voyage repairs, Thresher subsequently rendered target training services out of Pearl Harbor and Eniwetok. She was operating out of the latter base on 15 August 1945 when news of Japan's surrender reached her.

 

Thresher cleared Eniwetok on 15 September, arrived at Pearl Harbor seven days later, and stood out of Hawaiian waters on the 26th. Making port at San Francisco, Calif., on 4 October, the submarine subsequently left the west coast on the 31st. She transited the Panama Canal on 10 November and arrived at Portsmouth, N.H., eight days later. She was placed out of commission there on 13 December 1945.

 

The veteran submarine was recommissioned on 6 February 1946. She remained at her berth while her reduced complement prepared the ship for a voyage to the Pacific where she was slated for use as a target in Operation "Crossroads," the atomic bomb tests at Bikini Atoll in the Marshall Islands. However, during the refurbishing, it was decided that the ship had deteriorated beyond economical repair, and work was stopped. Thresher was decommissioned for the final time on 12 July 1946. Her name was struck from the Navy list on 23 December 1947, and she was sold for scrapping on 18 March 1948 to Max Siegel of Everett, Mass.

 

Thresher received 15 battle stars and a Navy Unit Commendation for World War II service.