His father had a distinguished career in the British Army including appointments as director of artillery at the War Office (1930 to 1934) and in India (1934 to 1938).[9] Hezlet later recalled having carried out about fifteen simulated attacks in elderly submarines in the Clyde on various kinds of mainly unsuitable target, following which it was declared he had passed.[9] On 22 December 1940 he took command of the obsolete coastal submarine HMS H44, spending three months in her, until 9 March 1941, tasked with training convoy escorts in anti-submarine warfare.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.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] When she arrived she was quickly ordered out to patrol the Bay of Biscay because it was feared that the German battleships Scharnhorst and Gneisenau, and the heavy cruiser Prinz Eugen, all lying at Brest, were imminently to come out.[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.[1] He invented the "Hezlet Rail", a bar and strap to secure the watchkeeper to the X-craft's casing in bad weather.[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.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.[25][26] Hezlet undertook long-range patrols in the Indian and Pacific oceans, earning him his first Distinguished Service Order (DSO).[25] On 8 June 1945, Hezlet took Trenchant into shallow mined water in the Banka Strait off Sumatra, to intercept Japanese heavy cruiser Ashigara.[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.The task of the Flag Officer Submarines was to help formulate plans for support and training facilities in a force as yet unfamiliar with nuclear propulsion.