Patrols in HMS Upholder and HMS Unique

In mid-summer 1941, it was considered by the flotilla command that the operational submarine commanders were becoming fatigued.^[9] Hezlet was sent on two patrols as relief for commanders who needed rest. The first began on 6 June 1941 when he was sent out in HMS Upholder, Lieutenant Commander Malcolm Wanklyn's boat, which ended on 17 June 1941 and was uneventful.^[9][12] The second began on 16 August 1941, when he took out HMS Unique in order to give its commander, Lt. Collett, a rest.^[9][13] That patrol would prove more testing. Unique and HMS P32 and HMS P33 were tasked with attacking a convoy off Tripoli. P33, unbeknownst to Hezlet at the time, had already hit a mine and had been lost with all hands.^[9] On 20 August Unique and P32 attacked. Hezlet fired four torpedoes – his first-ever torpedo attack on the enemy^[6] - at the 11,398 GRT Italian troop ship Esperia and sank her. Upon launching torpedoes from a U-class submarine, the commander had to ensure that the buoyancy caused by the torpedo tubes being filled with air did not cause the submarine to surface. He also had to get the submarine away from the end of the "tracks" made by the torpedoes moving through the water, because they would provide a visible indication to observers on the surface, and in the air, of the location of the submarine which had fired them. Hezlet was so preoccupied with these two tasks that he did not himself hear the torpedoes hit but was assured by the general jubilation in the control room that they had.^[9] An attack on Unique by an Italian flying boat later that day damaged one of her fuel tanks, and so Hezlet returned early from patrol. Upon his return to Malta, he learned that both P33 and P32 had been lost, making Unique the only submarine to survive the mission.^[9] Hezlet turned Unique back over to Lt. Collett and resumed his duties as spare CO.^[9] In November 1941 Hezlet was awarded the Distinguished Service Cross for the sinking of the Esperia.^[1][6][14]

HMS Ursula (N 59)

In September 1941 Hezlet was given his first permanent command – HMS Ursula^[11] - after her captain went sick. Of his six patrols in her, two merit reference, though neither resulted in her sinking an enemy ship. The first began on 16 September 1941, when Ursula was sent as part of a task group with HMS Upholder, HMS Unbeaten and HMS Upright to attack a convoy off Tripoli. Ursula was posted about 50 miles away from the main night-attack by the other submarines in order to carry out a daylight attack in the morning. Hezlet fired one torpedo at the Italian troopship Vulcania, but it was a long-range shot and missed. Upholder had more luck earlier that morning, successfully sinking the Italian merchant ships Neptunia and Oceania in that convoy.^[9][15] The second patrol saw Ursula head for the Strait of Messina, where she fired four torpedoes at two merchant vessels, damaging the Italian merchantman Beppe.^[15] The noteworthy feature of that patrol was that, from leaving Malta until and including launching her torpedoes, Ursula kept exactly the same course without deviating.^[9]

HMS Trident (N 52)

In late March 1942 Hezlet was given command of HMS Trident, the boat in which he had been First Lieutenant at the beginning of the war,^[9][10] with Ian McGeoch as his first lieutenant.^{[11][citation needed]} After brief exercises in the Clyde, Trident embarked on her first patrol under Hezlet's command to Norwegian waters, off Trondheim.^[10] Hezlet later recalled that his instructions were not to fire at anything but Tirpitz, which had arrived at Trondheim on 13 March 1942, and that he consequently had a frustrating time watching hundreds of thousands of tonnes of unescorted shipping plying the coastal waters.^[9] That appears potentially open to doubt because patrol reports appear to indicate that Hezlet made two attacks against merchant ships during that patrol, one unsuccessful but the latter, on 20 April 1942, resulting in his sinking of the German merchant ship Hödur, which he hit with two out of three torpedoes fired.^[10] The target sank in less than 5 minutes.^[10]

After further brief exercises in the Clyde in early May, Trident was ordered to Iceland to meet and escort convoy PQ16 to northern Russia.^[1][9][10] She was one of two submarines assigned to this duty, the other being HMS Seawolf.^[16] This eventful patrol saw Trident pick up nine survivors from the American merchantman Alamar which had been abandoned due to air attack (and carry out orders to torpedo its remains) as well as try to fend off other air attacks using her anti-aircraft guns.^[10] The convoy underwent five days of air attacks from Luftwaffe aircraft as well a submarine attacks. Of the 35 ships which left Iceland, 8 were lost.^[17] After a short anti-U-boat patrol from Polyarnoe, in June 1942 Trident was tasked with providing cover to convoys QP 13 and PQ 17 in the Barents Sea and Norwegian Sea, before returning to the UK.^[10] In August 1942, Hezlet was mentioned in dispatches for his service in escorting these convoys.^[6][18]

X-craft crew instructor

Hezlet became a special training officer on the banks of the River Clyde in September 1942, at the informally named "HMS Varbel", training the crews of midget submarines to attack the German battleship Tirpitz.^[1] He invented the "Hezlet Rail", a bar and strap to secure the watchkeeper to the X-craft's casing in bad weather.^[19]

HMS Thrasher (N 37)

In May 1943, Hezlet was appointed as the Lieutenant in Command of HMS Thrasher (N 37).^[20] From May to August 1943 she took part in exercises in Scottish waters with one-man Welman submarines and X-class "midget" submarines, undergoing alterations to her casing to allow her to operate with those craft.^[21] Finally, on 11 September 1943 Thrasher departed "Port HHZ" (Loch Cairnbawn) towing submarine X5 as part of Operation Source, the attempt to destroy Tirpitz, then lying at anchor in Kåfjord. Thrasher succeeded in towing X5 to her point of departure, though it is unclear how close X5 made it to her target: she was lost with all hands in the fjord during the attack. Thrasher returned to Holy Loch on 5 October 1943. Hezlet was mentioned in dispatches for his role in the operation (gazetted 11 January 1944).^[6][22]

In October 1943, before leaving Thrasher at Holy Loch, Hezlet was promoted to Lieutenant Commander six months early (at that time promotion to Lieutenant Commander was automatic after eight years as a Lieutenant^[23]) with eighteen months' seniority, as from 1 October 1942 (gazetted on 8 November 1943).^[6][24]

HMS Trenchant (P 331)

On 15 October 1943 Hezlet took over as Lieutenant Commander in Command of the submarine HMS Trenchant at Chatham.^[6][25]

After trials in the Clyde and nearby lochs, on 14 May 1944 Trenchant departed Holy Loch for Trincomalee, Ceylon (now Sri Lanka).^[6][25] Trenchant's first war patrol began on 25 July 1944 when she departed Trincomalee for the west coast of Sumatra. Her mission was partly to participate in Operation Boomerang, the USAAF's B-29 raid on oil fields and refineries at Palembang, by standing off the coast and assist in searching for and rescuing aircrew downed over the sea.^[9][25] Trenchant was given a special "homing device" to allow any B-29 in trouble to find her.^[26] In the event, no aircraft called for her assistance, though she was ordered to search for a downed aircraft but this proved fruitless.^[26] Trenchant was also to attack any enemy forces encountered. During the patrol she sank a Japanese coaster. Hezlet stopped to pick up survivors who were being discouraged by one of their number, an officer, from doing so. Hezlet manoeuvred Trenchant to cut the officer off from the rest of the group and eventually Trenchant managed to coax 14 Japanese to accept rescue; the others had to be left to their fate.^[25][26]

Hezlet undertook long-range patrols in the Indian and Pacific oceans, earning him his first Distinguished Service Order (DSO). He sank the long-range German U-boat U-859,^[1] on 23 September 1944, near the Sunda Strait, whose position had been identified through 'Ultra' signals decrypts.^[9]

On 27 October 1944, Trenchant deployed two Mk II Chariot manned torpedoes 6.5 nautical miles off Phuket in Thailand on a mission to destroy two salved former Italian merchant ships in what would prove to be one of the most successful uses of Chariots of the whole War. One Chariot, codenamed "Tiny" (manned by T/S.Lt. A.W.C. Eldrige, RNVR and T/A/Petty Officer S. Woollcott) was to target the former Sumatra, while the other, codenamed "Slasher" (manned by T/Petty Officer W.S. Smith and Ordinary Seaman A.F. Brown) was to target the former Volpi. Both Chariots successfully placed the charges on their target and proceeded back out of the harbour and the crews were re-embarked aboard Trenchant. Both targets were sunk. The chariots "Tiny" and "Slasher" had to be scuttled due to the danger from a Japanese patrol boat in the vicinity.^[25]

On 8 June 1945, Hezlet took Trenchant into shallow mined water in the Banka Strait off Sumatra, to intercept Japanese heavy cruiser Ashigara. Despite being attacked by the Japanese destroyer Kamikaze, five out of eight torpedoes that he fired hit Ashigara, which quickly sank.^[1] It was the largest Japanese warship sunk by a Royal Navy warship during the war.^[1]

Hezlet was ordered to Subic Bay in the Philippines, where he was awarded the U.S. Legion of Merit^[1] by U.S. Admiral James Fife, Jr. He was also awarded a Bar to his DSO.

Ordered to return to the UK, he ended the war as he began it, serving on a submarine.^{[citation needed]}