Interior of a Type A Japanese midget submarine.
Date: 29–30 May 1942
Attack by: Japanese Type A midget submarines
Target: British warships at anchor
On 30 April 1942, Admiral Ishizaki sailed from Penang, northwest Malaya, in I-10, a Type A1 boat designed to function as the headquarters of a submarine pack and carrying a Yokosuka E14Y1 (“Glen”) reconnaissance seaplane. With I-10 sailed I-16, I-18 and I-20, each carrying a Type A midget. On 5 May they refueled at sea from the armed merchant cruiser Hokoku Maru, in preparation for a cruise off southern Africa in search of suitable targets for the Type As. At dusk on 20 May, I-10’s aircraft scouted Durban, and on succeeding nights made similar fruitless searches for major warships at East London, Port Elizabeth and Simonstown. Farther north, a seaplane from I-30 hunted for heavy units of the British Eastern Fleet at Aden, Djibouti, Zanzibar, Dar-es-Salaam and Mombasa.
In November 1941, under German pressure, Laval’s Vichy French government had agreed in principle to Japanese occupation of the island of Madagascar, off the east coast of Africa. Although there was little chance of a fullscale Japanese takeover of the huge (227,602 sq mile, 589,489 sq km) island, the Allies could not ignore the threat to the Indian Ocean supply routes that a Japanese presence at the well-equipped French base of Diégo-Suarez, at the island’s northern tip, would pose. Thus, on 5 May 1942, the British launched “Operation Ironclad”, an amphibious attack on Diégo-Suarez against determined but short-lived Vichy French opposition. By the end of May the base had been secured and most of the invasion fleet’s warships had dispersed. There remained, however, a force consisting of the battleship HMS Ramillies, three destroyers and two corvettes.
At 2230 on 29 May, I-10’s seaplane flew over Diégo-Suarez Bay and returned to report “one ‘Queen Elizabeth’ class battleship and one cruiser at anchor”. The reconnaissance flight was spotted by the British, who suspected that it was a French plane scouting for Vichy French submarines believed to be still active in the area. At 0500 next morning, the most likely time for a submarine attack, Ramillies weighed anchor and kept moving around the bay until full light, while Fleet Air Arm aircraft flew anti-submarine patrols.
Admiral Ishizaki’s midgets were launched at dusk on 29 May. The Type A carried by I-18 proved to be unserviceable, so the attack was to be made by midgets from I-16 (crewed by Ens Katsusuke Iwase and PO Kozo Takada) and I-20 (Lt Saburo Akeida and PO Masami Takemoto). Like Iwasa, lost at Pearl Harbor, Lt Akeida had been a test pilot during the development of the Type A and was a volunteer for operational duty with the weapon.
It was obvious that the midgets had no chance of returning: launched 10nm (11 miles, 18km) out to sea, they were expected to pass undetected through the 1,300yd (1,190m) wide Oronjia Passage and navigate a channel some 8nm (9 miles, 15km) long, notorious for reefs, rocks and treacherous currents, before reaching the main anchorage at Antisirane. After making their attacks, the crews were ordered to scuttle their craft and return to the parent boats as best they could – presumably by making their way overland to a coastal rendezvous specified in advance.
It is believed that only one Type A penetrated the anchorage, the other having been lost without trace on the voyage in. The first indication the Royal Navy received of an intruder came at 2025 on 30 May, when a torpedo struck Ramillies on the port bulge forward of ‘A’ turret, causing extensive damage in the forepart of the battleship. A short time later, another torpedo struck the tanker British Loyalty (6,993 tons, 7,105 tonnes), which sank almost immediately. The British corvettes immediately got under way and combed the bay throughout the night, making frequent depth charge attacks. Although no confirmed contact was made, the Type A was probably damaged, for by morning it had been abandoned by its crew and had drifted on to a reef, where it was discovered in a wrecked condition some two weeks later.
Ramillies, with a 900 sq ft (84 sq m) hole torn in her bulge and a 320 sq ft (30 sq m) rent in her outer bottom, rapidly took water in her forward magazines and compartments and began to settle by the bow. Rapid discharge of oil fuel and offloading of ammunition restored her trim and, with her main machinery undamaged, she was able to steam for repair to Durban, where she remained out of action for nearly one year. British Loyalty had settled in shallow water and was raised and repaired. It was at first thought that the attack had been made by a Vichy French submarine, but a few nights later the two Japanese crewmen were cornered ashore by a Commando patrol and, refusing to surrender, were shot dead. Had the attacker been identified at once as a Japanese midget submarine, and an immediate report sent to other Allied bases, Allied naval units might have been spared a severe shock less than one day later, when the Type As struck at Sydney, Australia.