After completing training, Robalo set a course for Pearl Harbor, Territory of Hawaii, on 3 December 1943. Upon her arrival in the Hawaiian Islands on 17 December 1943, Robalo underwent four days of repairs, followed by additional exercises and a sound test. Lt. Cmdr. Armbruster’s falling ill and departing for treatment resulted in Lt. Cmdr. Charles W. Fell, the executive officer, assuming temporary command when she stood out en route to Midway Atoll at 1330 on 8 January 1944, escorted until darkness fell by the submarine chaser PC-581. During her two-day trip, the submarine conducted daily trim dives as well as multiple drills, arriving at Midway to begin refueling at 0915 on 12 January. As Robalo refueled and prepared for her first war patrol the following afternoon, Armbruster returned to the submarine and resumed command at 1640.
Robalo departed Midway at 0940 with local air cover on 14 January 1944, and set course for her patrol area off the west coast of the Philippine Islands. The submarine entered her designated hunting ground, submerged, and began patrolling at 0531 on 27 January. Unfortunately, over the next five days she found the waters from the San Bernardino Strait to the Surigao Strait devoid of enemy ships.
At 1945 on 1 February 1944, Robalo proceeded eastward into the strait en route for Binit Point, Leyte, Philippine Islands (P.I.). Less than two hours later at 2122, her radar detected a contact 9,600 yards to the west. Despite increasing her speed to 14 knots, her prey unfortunately pulled further away and forced the submarine to abandon the chase and resume her previous course at 2210.
Robalo completed transit of the Surigao Strait and began patrolling south of Binit Point at 0255 on 2 February 1944. Later that evening at 1943, she took advantage of the calm waters off Limasawa Island to retune her radar as well as remove 14,000 of lead ballast. The submarine completed maintenance at 0200 on 3 February and proceeded westward.
As she steamed on the surface of the Cebu Strait at 2135 that evening, Robalo sighted two Japanese warships she believed to be destroyers on course 025°T at a range of 16,000 yards. Unfortunately, as the submarine maneuvered ahead of the enemy “tin cans,” they unexpectedly turned westward and closed on Cebu, P.I. Unable to engage in a high-speed surface chase because of the evening’s significant moonlight, Robalo lost contact with the enemy at 2222.
At 1639 on 13 February 1944, Robalo detected the two vessels—Minryu Maru and Sekino Maru—of Japanese convoy MO-72 steaming in column on course 310°T en route to Manila, escorted by Patrol Boat No. 103 (ex-Finch (AM-9), a minesweeper that had been recovered by the Japanese from the waters off Corregidor and reconditioned for service.) Robalo selected the Japanese Army cargo ship Sekino Maru as her target, maneuvered to within 3,100 yards, and fired four Mk. XIV torpedoes at position 13°30'N, 121°13'E at 1729. Believing that one of her four “fish” struck the enemy vessel, Robalo maneuvered into a new firing position, but as she did so Patrol Boat No. 103 quickly converged on the submarine’s location and fired 13 depth charges from her Type 91, Mk. 1 depth charge projector from 1745-1755.
Undamaged, Robalo remained deep for nearly two hours, eventually coming up to radar depth at 1928. Failing to detect an enemy presence via both her periscope and radar sweep, she surfaced approximately five minutes later and sighted Patrol Boat No. 103 on her starboard quarter only 2,000 yards distant. A depleted battery forced the boat to remain on the surface as she attempted to retire from the area. As she widened the distance between herself and the enemy vessel another 500 yards, the ex-minesweeper opened fire with her 3-inch/40 gun. Fortunately, each of the 25-30 shells hurled at the escaping submarine over the next half hour exploded well to starboard. Robalo finally broke contact with Patrol Boat No. 103 and proceeded to the waters off Marinduque, P.I., at 2025.
After an unsuccessful day patrolling off Marinduque, Robalo submerged at 0550 on 15 February 1944 and steamed into the Sulu Sea. Three days later the submarine detected an enemy cargo vessel escorted by an unidentified warship at a range of 24,000 yards. Despite giving chase over the next half hour, Robalo was only able to close to within 18,000 yards before losing contact with the two vessels at 0745. Later that evening, she steamed southward and began patrolling off Cagayancillo Island, P.I. Unfortunately the submarine found the Sulu Sea completely barren of potential enemy targets, terminated her patrol and set course for the submarine base at Fremantle, Australia at 1928 on 22 February 1944.
As she proceeded southward on 29 February 1944, at 1430 Robalo heard the distinctive “ping” of active sonar on bearing 270°. Despite exposing 17 feet of her periscope, she was unable to locate its source, which gradually drew aft until the submarine eventually lost contact on bearing 290°T. A few hours after she surfaced for the evening at 1900, she detected a vessel on bearing 192°T, at a range of 5,800 yards, just north of the entrance to Lombok Strait. Unfortunately, poor visibility prevented her from developing the contact. She entered the strait at 0041 on 1 March and continued her voyage southward. Five days later, Robalo moored at Fremantle at 0600. She was immediately assigned to Submarine Repair Unit 137 for refit but would not remain in port for long.
In response to the movement of a large enemy force including two battleships and two aircraft carriers from the Japanese naval base at Singapore on 4 March and the detection of the light cruisers Kinu and Oi in the Lombok Strait two days later, Rear Adm. Ralph W. Christie, Commander Submarines, Southwest Pacific Area, ordered his boats to be made ready for sea at 2300 on 7 March 1944. Robalo stood out in search of the enemy in company with Flasher (SS-249), Hake (SS-256, Hoe (SS-258) and Redfin (SS-272) the next evening at 2100. The expected Japanese assault on Australia, however, never materialized and the U.S. boats returned to port on 14 March.
After she returned to port following the emergency deployment, Robalo’s officers and crew enjoyed two weeks of leave as SRU 137 overhauled their boat’s No. 1 and No. 2 engines. On 29 March 1944, Lt. Cmdr. Manning M. Kimmel, son of Adm. Husband E. Kimmel, who had been in command of the U.S. Pacific Fleet at the time of the Japanese attack on the fleet on 7 December 1941, relieved Lt. Cmdr. Armbruster in command. The submarine subsequently underwent several days of loading and training exercises from 31 March—9 April. She stood out to sea and set course for Darwin, Australia, the next day.
Robalo’s first day at sea, she conducted multiple exercises with Bonefish (SS-223) and an unidentified convoy. After the two submarines parted at 2400 that night, Robalo continued conducting training dives and exercises over the next five days. Unfortunately, her voyage to Darwin was slightly delayed by a cracked liner that put her No. 2 engine out of commission from 0100-1515 on 16 April 1944. She finally rendezvoused with the escort vessel ML-809 at 0540 the next morning and moored in Darwin Harbor approximately three hours later. The submarine completed refueling and got underway for her patrol area at 1438.
Robalo entered the South China Sea and passed south of the dangerous ground at 2400 on 22 April 1944. Approximately a half hour later, the submarine detected a contact steaming 7,000 yards to the southwest. Over the next six minutes, the two vessels closed to within 3,200 yards, whereupon Robalo determined the contact to be a submarine. Suspecting that another American boat might be in the vicinity, she reversed course and lost sight of the contact at 0100. The submarine entered her patrol area off French Indochina [Vietnam] at 0930.
While running on the surface at position 10°29'N, 109°E at 1830 on 24 April 1944, Robalo sighted what she identified as a Japanese Mitsubishi G4M Type 1 land attack plane [Betty] flying a parallel course bearing 330°T less than two miles off the submarine’s port beam. As she dove to avoid the enemy aircraft, the submarine heard the first of two 250-kg.bombs dropped by the enemy aircraft explode off her conning tower. As she reached 55 feet below the surface, the boat shook violently as the second Japanese bomb detonated off her port side forward compartment. Interestingly, at around the same time attack planes from the escort carrier Kaiyo carried out an attack on the embattled boat, making it difficult to assign credit for damage to one or the other Japanese aerial agent. Shortly thereafter, the Etorofu-class escort ship Iki arrived with the Type C escort vessel CD-9 and began launching depth charges. Luckily, the submarine easily evaded both ships and avoided further damage.
When the boat eventually leveled off at 350 ft., an initial assessment revealed damage to her JP radar significant enough to render it inoperable, as well as severe damage to her hydraulic steering. The attack also left Robalo with relatively minor leaks in her conning tower hatch, No. 1 main vent, pit log and antenna trunk.
In addition to her internal damage, an external inspection of the submarine conducted as she steamed out of the area at 2013 found her port and center antennas broken and No. 1 periscope flooded. Her 4-inch gun, main ballast tanks and auxiliary engine exhaust valve were less severely damaged.
After spending the night conducting repairs, Robalo submerged and began an internal inspection of the boat at 0545 on 25 April 1944. The inspection found the submarine in satisfactory condition, which allowed her to remain on patrol. She surfaced again several hours later at 1910 and set course for the coast of Indochina to conduct further repairs on her SJ radar. The submarine made landfall on Ile des Pêcheurs [Hôn Ngoąi], Indochina, and began repairs at 0330 on 26 April. Unfortunately, she was unable to repair her damaged radar.
At 0806 that morning, Robalo sighted a convoy of three Japanese merchant vessels escorted by two warships steaming on bearing 270° at position 12°0'N, 109°19'E. The submarine immediately went to battle stations and closed on the contact. Unfortunately, she was only able to maneuver to within 11,000-12,000 yards and secured from battle stations at 0930. She closed on the Indochina coast, surfaced for the night at 1947 and finally successfully repaired her radar. Despite this success, she failed to detect a significant enemy ship for the remainder of the month.
As Robalo patrolled off Phan Rang [Phan Rang-Tháp Chàm] at 1150 on 2 May 1944, she detected two steamers at position 11°29'N, 109°11'E, bearing 267°T. Unfortunately, she was only able to close to within 5,200 yards and aborted the attack at 1328. Less than a half hour later, she detected another merchant ship steaming at eight knots on course 190°T. The submarine briefly closed on the enemy vessel before determining it too small to be worth an attack.
At 0738 the next morning, Robalo sighted smoke at 11°58'N, 109°19'E that developed into a convoy of three merchant vessels escorted by two warships. The submarine maneuvered herself into a position 12,000 yards from the leading merchant vessel and began her attack run. At 0848, she fired the first of six torpedoes at a range of only 750 yards from her prey. Unfortunately, all six missed their intended target and were sighted by one of the enemy escorts, which immediately set course for Robalo. The submarine dove to 170 ft. as the first of five depth charges exploded overhead. As the enemy escorts pinged intermittently, the submarine remained in deep water for over an hour.
Robalo began ascending once again at 1014. As she reached 80 ft., the nearby detonation of four bombs forced her deep once again. Another depth charge attack followed from 1232-1253, during which she developed a leak her port side main induction valve. The submarine finally rose to periscope depth at 1612 and cleared the area at 2135.
Three days later on 8 May 1944, Robalo began tracking a submarine bearing 250°T on course 12°13'N, 113°40'E at 0705. Shortly after going to battle stations at 1412, she determined her prey to be a Japanese I-class boat. Over the next 45 minutes, the American boat crept to within 1,500 yards and fired four torpedoes from her stern tubes. A minute later, the Japanese submarine swung left, parallel to the track of Robalo’s four fish. Apparent that she had missed her target, Robalo dove to 90 feet. Five minutes later, she heard three metallic clicks or small explosions, followed by three larger explosions of what she believed to be torpedoes. She returned to periscope depth at 1525 and observed the Japanese submarine steaming away on bearing 347°T. Rather than pursue the target, she chose to surface and resume patrolling her assigned area at 1805.
As Robalo continued her patrol she sighted and investigated a piece of bulkhead with two doors, clothing, ship piping and a small life raft floating at position 13°09'N, 113°09'E at 1050 the next day. Over the next three days she detected six small steamers, none of which she judged worthy of attacking. The submarine completed patrolling the area and set course for the “Dangerous Ground” at 0045 on 15 May 1944.
Robalo began patrolling near the “Dangerous Ground” shortly after 0800 on 16 May 1944. Approximately four hours later, the submarine sighted smoke on bearing 190°T. Shortly thereafter, she identified the source of the smoke as an enemy convoy on course 9°53'N, 115°41'E. Unfortunately, as she attempted to maneuver into position, a Kawanishi Navy Type 97 flying boat [Mavis] forced her to dive. Choosing to await nightfall before attempting another try, she remained submerged as the convoy of ten merchant ships escorted by three destroyers steamed northward.
Robalo surfaced and restarted her attack on the merchant convoy at 1910. She reacquired the enemy vessels as they steamed at position 10°29'N, 115°30'E approximately 45 minutes later. Finally able to maneuver into an advantageous firing position at 2347, she selected a large 7,500-ton tanker crept to within 3,200 yards and fired six torpedoes. As she swung to starboard, Robalo saw one of her fish strike the enemy vessel just aft of amidships. As the submarine cleared the area to avoid a depth charge attack from an enemy destroyer, she heard two explosions and believed her target sank.
Shortly after the Japanese convoy reformed on course 000°T at 0130 on 17 May 1944, Robalo lined up for another attack. As she closed to within 4,500 yards, an enemy destroyer suddenly changed course and closed on the submarine. Robalo quickly swung to starboard, brought her stern tubes to bear, and fired four torpedoes at the onrushing enemy ship at 0136. Unfortunately, as she fired, her prey turned once again, all four torpedoes missed and the enemy vessel caught the submarine in her searchlight, forcing Robalo to clear her bridge and dive.
Shortly after being forced to dive, Robalo heard the explosion of the first of 19 depth charges fired within just two minutes. Pinging, punctuated by an occasional depth charge fired by three or four enemy warships steaming overhead, continued until 0250. As the enemy attack ceased, Robalo found the repeated explosions had worsened a previously existing leak in her starboard main induction valve. This leak, combined with an occasionally malfunctioning periscope, forced Kimmel to terminate his boat’s patrol. Robalo surfaced at 1312 and set course for Australia at 1600.
Robalo uneventfully steamed through the South China Sea and Java Sea en route to Lombok Strait from 18–23 May 1944. A half-hour after she entered the strait at 2323 on 24 May, the submarine sighted a Japanese patrol boat on course 273°T. Rather than give chase, the submarine maneuvered west to avoid conflict with the enemy vessel. She detected her final contact of the patrol, Angler (SS-240), on bearing 355°T at 0320 on 27 May. Robalo ended her patrol and moored at Fremantle, Australia three days later. The submarine remained moored undergoing repairs and a refit until late June.
Robalo departed on her third war patrol en route to the waters off Natuna Islands, Indonesia, on 22 June 1944. On 3 July, the submarine reported to Commander Submarines, Southwest Pacific, that she had sighted the Japanese battleship Fuso escorted by air cover and the destroyers Michishio, Nowaki and Yamagumo off the east coast of Borneo at position 3°29'N, 119°26'E. Unfortunately, Navy officials in Australia received no further messages from Robalo and presumed her lost.
On 5 September 1944, Adm. Ernest J. King, Chief of Naval Operations, ordered Rear Adm. Freeland A. Daubin, Commander Submarines, Atlantic Fleet, to report to Seventh Fleet headquarters in Brisbane and conduct an investigation into the disappearance of Robalo as well as the 14 August loss of Flier (SS-250). The admiral traveled to the Pacific quickly and opened a Court of Inquiry just nine days later.
In his first day’s testimony, Cmdr. John D. Crowley, Flier’s commanding officer, told the court that in his effort to return to Allied custody after the loss of his boat he encountered Philippine Army Sergeant Pasqual de la Cruz at a guerrilla outpost at Cape Buliuyan, Palawan, P.I. on 31 August 1944. Sergeant de la Cruz had just returned from a reconnaissance mission undertaken in response to rumors that American military personnel had recently been taken prisoner by Japanese forces on Balabac Island, P.I. According to Crowley’s account of their conversation, de la Cruz reported that Robalo suffered an explosion in her forward battery compartment as she patrolled 40 miles west of Balabac and sank on 3 July. Lt. Cmdr. Kimmel, Ens. Samuel L. Tucker, SM3c Wallace K. Martin, and an unidentified fourth sailor were able to escape the doomed submarine and make their way to Comiran Island, Palawan, P.I., located several miles east of Balabac. Shortly after their arrival on the island, Japanese troops took two of the four sailors prisoner and interned them at the prison camp at Puerto Princesa, Palawan, P.I. Unfortunately, de la Cruz proved unable to determine the specific fate of any of the four submariners. Crowley testified, “the facts are not clear,” and opined that the Japanese had likely shot two of the sailors.
In his findings of fact, Rear Adm. Daubin determined that a mine, struck as the boat transited into Balabac Strait via Nausubata Channel during the night of 3-4 July 1944, might have caused the explosion in Robalo’s forward battery compartment. He also determined that the Japanese shot Kimmel and an unidentified sailor and took Tucker and Martin prisoner. On 23 September, Vice Adm. Thomas C. Kinkaid, Commander, Seventh Fleet, concurred with the court’s findings of fact and opinion on the loss of the submarine.
Shortly after the landing of American forces on Palawan on 28 February 1945, soldiers from the US Army’s 308th Counterintelligence Corps (CIC) searched the Japanese 14th Area Army Military Police Guard Unit headquarters and discovered documents that detailed the fate of Robalo and her crew.
According to the interrogations of EM2c Mason C. Poston and Ens. Tucker, an explosion rocked Robalo as she steamed in the Sulu Sea on the evening of 2 July 1944. The blast threw Kimmel, Lt. Cmdr. Fell, Poston, Tucker and six other sailors standing on the submarine’s deck into the ocean. Three unidentified sailors quickly drowned, while Kimmel, Fell and Tucker drifted westward toward Balabac Island together until just after midnight. Exhausted and only able to keep afloat by swimming on his back, Kimmel briefly joined QM1c Floyd G. Laughlin at 0900 the next morning before disappearing an hour later.
Stymied by strong currents and shifting wind, Poston and Martin finally reached tiny Comiran Island at 1100 on 3 July 1944, approximately 15 hours after they were thrown into the southwest Pacific. Tucker joined his shipmates at 1300, with Laughlin washing ashore an hour later. Surviving on a diet of rainwater, the sailors constructed a makeshift shelter and raft over the next three days. The submariners finally departed for Balabac Island at 1100 on 6 July. They reached their destination and made landfall near the Malaking Ilog River at approximately 0900 the next morning. Shortly after coming ashore, the sailors ate their first meal in several days in a nearby coconut grove before traveling into the island’s mountainous interior.
The submariners successfully evaded capture and roamed the mountains for the next 18 days, until unfortunately apprehended by the Japanese 33rd Naval Guard Unit on 25 July 1944, and taken to the 14th Area Army Military Police Unit (Kempeitai) headquarters in Puerto Princesa.
After nearly a month in the custody of the Kempeitai, the four submariners were taken to the Third Expeditionary Fleet headquarters in Manila on 19 August 1944 for further interrogation. According to Japanese records, the prisoners safely arrived at fleet headquarters and underwent interrogation on 25 August. Unfortunately, their subsequent fate is unknown.
Robalo was stricken from the Navy Register on 16 September 1944.
Robalo received two battle stars for her World War II service.
Date Assumed Command
Lt. Cmdr. Stephen H. Armbruster
28 September 1943
Lt. Cmdr. Manning M. Kimmel
29 March 1944
Christopher M. Martin
27 September 2021