X3 to X54: The History of the British Midget Submarine

PART ONE

X CRAFT

HISTORY

1

THE MEDITERRANEAN

In the early part of the Second World War, the Italians realised they couldn’t match the Royal Navy, and Mussolini’s efforts to seize control of the Mediterranean had, by late 1941, failed. The raid on Taranto and the Battle of Cape Matapan had given the Royal Navy a decisive advantage. Low morale and fuel shortages further impeded the Regia Marina’s capabilities. Nevertheless, the Italians still had several modern battleships and a few older, modernised vessels. Fortunately for the Italians, the Royal Navy had lost one of its battleships; a German U-boat had sunk HMS Barham on 25 November 1941 and the British had deployed several warships to the Far East in expectation of war with Japan.

Just before the outbreak of war, the Italians set up a special unit to develop innovative ideas to level the balance of power with the Royal Navy. In 1941, this unit became the 10th Flotilla (Xa MAS). They developed two primary/novel methods of attacking the British Mediterranean Fleet.

The first was a 2-ton, 18ft-long wooden speedboat packed with 728lb of explosives. It was powered by an Alfa Romeo AR 6cc Outboard Motor rated at 95hp and could reach speeds of 33 knots. It was known as the Motoscafo da Turismo (MT) and nicknamed Barchino (little boat). These boats were specially designed to make their way through obstacles such as torpedo nets. Once the operator aimed the boat at his target, he locked the steering and dived into the water.

The second weapon, which resulted from a collaboration between two young engineers in the Italian Navy’s Submarine Service, was the human torpedo, known as siluri a lenta corsa (SLC, or slow-speed torpedo).

This was not an entirely new idea. In 1918, days before the surrender of the Central Powers, the collapsing government of Austria-Hungary made clear that it would pass one of its dreadnought battleships, SMS Viribus Unitis, on to the newly created State of Slovenes, Croats and Serbs, a forerunner of Yugoslavia. The Italians did not want to see a powerful battleship falling into the possession of a potential regional rival; Italy believed the ship still belonged to Austria-Hungary and no peace treaty yet existed. Accordingly, a team of divers entered Pula Harbor and attached a mine to the bottom of the battleship. They were quickly captured and confessed to attaching the weapon without indicating the exact spot of its placement. But the Austrians couldn’t find the mine, which exploded and sank the battleship.

The early Italian vessels were electrically propelled and had a maximum speed of 3 knots and a range of up to 10 miles. Most of these vessels and others developed during the Second World War had hydroplanes at the rear, side hydroplanes in front, and a control panel. There were typically four flotation tanks, two to the front and two aft, which were flooded or blown empty to adjust buoyancy and attitude, as is the case on a submarine. The early vessels were equipped with a compass. In some later versions, riders’ seats were enclosed, and even domed cockpits were added. Most manned torpedo operations were conducted at night and during the new moon to reduce the risk of detection.

On 21 August 1940, the submarine Iride was attacked by three Swordfish from HMS Eagle while loading SLCs in the Gulf of Bomba in Libya. The submarine was sunk.

The first operational use of the SLCs was in September 1940, when eight were carried on board the submarines Gondar and Scirè, which sailed for Alexandria and Gibraltar. When Scirè arrived off Gibraltar, it found the harbour empty: HMS Renown, HMS Ark Royal and HMS Sheffield had sailed a few days earlier to help in the search for the Bismarck. While en route to Alexandria, the second submarine, Gondar, which was carrying three SLCs, passed the Mediterranean Fleet, which had left Alexandria, heading for Malta. Without viable targets, the submarine was rerouted to Tobruk. Before reaching its destination, it sighted an enemy ship and dived to avoid detection. However, it was quickly located by the destroyer HMAS Stuart and attacked. Two other ships joined the attack and the prolonged depth charge attack caused considerable damage to the submarine and the SLC units, which began to flood. It was forced to surface and the crew scuttled the vessel with explosive charges. All the crew but one was rescued and imprisoned.

The following month the Italian divers returned to Gibraltar but a rebreather problem prevented one team from approaching their target; another SLC sank. Finally, the third craft experienced a steering failure as it approached HMS Barnham. The two crew tried to drag the SLC into position but couldn’t and abandoned the craft. A few hours later, the warhead exploded without causing any damage, alerting the British to this new threat. More importantly for the British, several days later, one of the scuttled SLCs was washed ashore on a nearby Spanish beach. The British wasted no time in photographing it and some of the equipment from the craft was salvaged and sent to Britain.

These setbacks led to system improvements, intensified training, and the exploration of other attack methods.

By the end of 1941, Italy was struggling to supply the Italian and German armies in North Africa. British surface ships, aircraft and submarines were so successful in blocking Italian shipping that in November 1941 only 38 per cent of materiel (29,813 of 79,208 tons) sent to Libya arrived. The Italian high command planned several measures to help remedy this situation. These included changes to convoying patterns, the use of the battle fleet to escort convoys, and SLC attacks against the British naval bases at Alexandria and Gibraltar.

On 25 March 1941, the MT were used to attack the heavy cruiser HMS York off Souda Bay, Crete. The motorboats were launched by the destroyers Francesco Crispi and Quintino Sella on the approaches to the bay. After negotiating the boom defences, the small craft attacked York and the Norwegian tanker Pericles. Both vessels were sunk.

Scirè returned to Gibraltar on the night of 26/27 May 1941 and launched three SLCs. One sank; the others reached merchant shipping anchored in deep water outside the military harbour but mechanical failures stopped them placing their charges.

On the night of 19 September 1941, Scirè launched three SLCs in the Bay of Gibraltar. Italian intelligence had reported that a battleship, an aircraft carrier and two cruisers were in the military harbour. Unfortunately for the Italians, after the earlier unsuccessful attack, the British were now more aware of this new Italian threat and better prepared to counter it. As a result, the Algeciras roadstead and the entrance to the military harbour were patrolled regularly by harbour launches, which dropped depth charges at regular intervals.

Due to the frequent patrols, the first SLC could not enter the military harbour. With dawn approaching, the crew decided to attack a merchantman and fixed their warhead to a sizeable nearby ship. Realising their intended target was an Italian-registered, captured vessel, they detached the charge and transferred it to another armed merchantman, Durham. The SLC crew scuttled their craft and swam to safety on the Spanish shore. The resultant explosion badly damaged Durham and it had to be beached by harbour tugs.

The second SLC also had trouble with the patrolling harbour defence vessels and chose a target in the roadstead. Their targets broke in half when the warhead exploded.

The third SLC managed to penetrate the heavily defended anchorage. Once inside, the crew decided they did not have the time to search for HMS Ark Royal and decided to attack a large tanker in the hope that a large fire would ensue and engulf the harbour. The resultant explosion broke the back of the Royal Fleet Auxiliary oiler Denbydale; the hoped-for inferno did not happen.

Shortly after this mission, the Italian Navy began work on Oterra, a tanker that had been scuttled in the harbour of Algeciras, Spain, which was within sight of Gibraltar. The Italians told the Spanish that they were cleaning the ship’s trimming tanks and ensuring its neutrality. Next, the ship’s bow was raised and a hatch was cut in the hull, which led to a watertight compartment. When the work was completed, the bow was submerged, which put the new compartment and the watertight hatch under the water. The Italians then told the Spanish they were moving in boiler tubes to repair the engines so the ship could be moved after the war; instead, they loaded several 22ft manned torpedoes.

Starting in early December 1942, the ship was used as a base to launch several attacks on Allied shipping, usually in open anchorages.

On 8 December 1942, three SLCs attacked British naval targets; the British harbour defence ‘reacted furiously’ to the attack, dropping depth charges, and three divers were killed. On 6 May and 10 June 1943, Italian SLCs from Oterra sank six Allied merchant ships.

A large-scale operation was conducted 26 July 1941, when MAS 451 and 452 (24.5-ton motor torpedo boats) accompanied by a 1.9-ton, two-man MTS torpedo boat, nine 1.3-ton MTM crash boats and two SLCs (carried on board an adapted motorboat called an MTL) attacked the Grand Harbour breakwater in Malta.

British radar had detected these craft well before they reached their destination, and the Italians were met with a fierce pre-warned and prepared opposition. Apart from the MTS, all the craft were lost, fifteen personnel were killed, including the unit’s commander, and eighteen were captured.

A major operation was launched on 3 December 1942, when Scirè, carrying three SLCs, sailed from Italy. On 19 December, it made a submerged approach to Alexandria harbour, where the battleships HMS Queen Elizabeth and HMS Valiant were anchored. Italian intelligence had mistakenly reported that an aircraft carrier would be in the port.

Once in position, Scirè launched the SLCs. One team successfully attached a mine to the hull of Queen Elizabeth and another attached its mine to a large oil tanker. The final team, despite mechanical problems both with their breathing equipment and with the SLC itself, secured their charge to Valiant.

The resultant explosions caused considerable damage. Queen Elizabeth sank into the mud, although it remained upright; Valiant was seriously damaged but did not sink. The tanker Sagona was severely damaged, and a British destroyer, HMS Jervis, which was fuelling alongside it, also suffered severe damage. Queen Elizabeth took nine months to repair; Valiant six. Jervis was repaired and operational by the end of January. Sagona was towed back to England, although the repairs were not completed until 1946.

Overnight, the Italians had eliminated two of the Royal Navy’s most powerful ships in the Mediterranean and at minimal cost to themselves. The attacks on Gibraltar were a nuisance. Malta showed, or so the Admiralty believed, that the human torpedoes were no real threat but this was very different. This attack represented a dramatic change in Italian fortunes and would affect British tactics from a strategic point of view during the next six months. The Italian fleet had temporarily wrested naval supremacy