The XE-class submarines were a series of six midget submarines that were built for the Royal Navy during 1944. They were an improved version of the used in the attack on the Germanbattleship. They carried a crew of four, typically a lieutenant in command, with a sub-lieutenant as deputy, an engine room artificer in charge of the mechanical side and a seaman or leading-seaman. At least one of them was qualified as a diver. In addition to the two side charges, they carried around six limpet mines which were attached to the target by the diver. They and their depot ship arrived at Labuan in July 1945. Four of them managed to take part in operations before the war ended.
''Sabre'' and ''Foil''
These operations, carried out in July 1945, were intended to cut the undersea telephone cables connecting Singapore, Saigon, Hong Kong and Tokyo. The intention was to oblige the Japanese to use radio and render themselves open to message interception. Operation Sabre was directed at the Hong Kong to Saigon telephone cable, and carried out by XE4, which was towed to within of the Mekong Delta by the submarine HMS Spearhead, where she looked for the two telephone cables by using a towed grapnel. She eventually snagged the first cable, and managed to haul it about off the seabed. XE4's diver, Sub-Lieutenant K.M. Briggs, used the net/cable cutter to sever it. The second cable was soon found as well, and was severed by the second diver, Sub-Lieutenant A. Bergius. Two divers were carried due to the operating rule that a diver should not spend more than 20 minutes in depths over and no more than 10 minutes over. XE4 and Spearhead returned to Labuan on 3 August 1945. Operation Foil was directed at the Hong Kong to Singapore telephone cable and carried out by XE5 against the Hong Kong end of the cable, after being towed into position by the submarine HMS Selene. Operating close inshore near to Lamma Island, working conditions were poor, XE5's divers having to work in thick mud under the constant threat of oxygen poisoning. Despite repeated attempts it was not completely certain that the cable had in fact been severed, and it was not until after the Japanese surrender that it was confirmed that XE5 had succeeded in doing so. XE5 and Selene returned to Subic Bay on 6 August 1945.
Operation Struggle
In August 1945, HMS XE1 and XE3 executed a joint attack on Japanese warships within Singapore harbour. XE3 was tasked with mining the heavy cruiserTakao while XE1 was to attack the heavy cruiser Myōkō. The approach of XE3 along the Straits of Johor and through the various harbour defences took 11 hours plus a further two hours to locate the camouflaged target. Despite several opportunities for Japanese defenders to spot the vessel, XE3 successfully reached the Takao, fixed limpet mines and dropped its two, 2-ton side charges. The withdrawal was successfully made and XE3 returned to HMS Stygian, her towing submarine. Meanwhile, XE1 was delayed by Japanese patrol craft, and her captain, realizing that he could not reach Myōkō before the mines already laid by XE3 would explode, also elected to drop his own charges under Takao. XE1 also successfully returned to her towing submarine, HMS Spark. The Takao, already damaged and not seaworthy, was severely damaged and never sailed again. XE3s commander, LieutenantIan Edward FraserRNR, and diver Leading SeamanJames Joseph Magennis were awarded the Victoria Cross for their part in the attack; whilst Sub-Lieutenant William James Lanyon Smith, RNZNVR, who was at the controls of XE3, received the Distinguished Service Order ; Engine Room Artificer Third Class Charles Alfred Reed, who was at the wheel, received the Conspicuous Gallantry Medal. XE1's C/O, Lieutenant John Elliott SmartRNVR received the DSO, and Sub-Lieutenant Harold Edwin Harper, RNVR received the Distinguished Service Cross ; and ERA Fourth Class Henry James Fishleigh and Leading Seaman Walter Henry Arthur Pomeroy received the Distinguished Service Medal. ERA Fourth Class Albert Nairn, Acting Leading Stoker Jack Gordan Robinson, and Able Seaman Ernest Raymond Dee were Mentioned in Despatches for their part in bringing the two midget submarines from harbour to the point where the crews that took part in the attack took over.
XE10 — built by Markham, cancelled incomplete 1945
;Second group
XE11 — built by Marshall, collided with boom defence vessel in Loch Striven after drifting out of her exercise area and lost 6 March 1945. Three crew were killed in the accident but two managed to escape. The boat was later salvaged.
XE12 — built by Marshall, cannibalised for spares 1952
