The Japanese midget submarine attack on Sydney Harbour was audacious and would have been even more spectacular had the primary military targets been successfully attacked. The attack showed the vulnerability of ports like Sydney to long-range submarine patrols and the need for heightened security. Many Sydney-siders still recall the moments at night on 31 May 1942 as the harbour lit up with depth charge explosions, tracer fire and cris-crossing sonar. The explosion as a Japanese torpedo struck the ferry HMAS Kuttabul was intense, throwing portions of the shattered hull high into the sky and killing twenty-one men.
The attack mirrored the earlier midget submarine operations at Pearl Harbour (7 December 1941) and the raid on Diego Suarez in Madagascar (30 May 1942). The Sydney raid involved five large ocean going submarines, I-22, I-24, I-27 with their three midget submarines, and I-21 and I-29 providing support. The five mother-submarines, which had left Truuk Lagoon, arranged themselves in a semi-circle centered on The Heads and spread from Broken Bay to South of Port Hacking. A previous flight (29 May) by a reconnaissance aircraft launched from I-21 has spotted potential targets inside the harbour. This Glen-type twin-float seaplane capsized when returning to its submarine and was scuttled. The remains have not been located.
At about 8pm on the Sunday evening, the first midget (number 14 from I-27) commanded by Sub Lieutenant Lieutenant Matsuo, motored submerged into the harbour. Unfortunately for its crew, the boat became fouled in the anti-submarine boom net laid across the harbour between Georges Head and Watson's Bay. Observed by surface craft, the two-man Japanese crew later committed suicide by detonating an internal scuttling charge about 10.30pm. Remains of this submarine were later recovered.
Midget A from I-24 (or M-24), commanded by Sub Lieutenant Ban entered the harbour and followed a Manly ferry through the boom defences. In a cat-and-mouse play, the submarine manoeuvred around the harbour and was sighted several times. Under fire from the US heavy Cruiser USS Chicago and several motor launches, the submarine successfully fired its two torpedoes about 11.30pm. Both missed Chicago - the prime target, one running onto Garden Island and failing to explode. The other struck the ferry HMAS Kuttabul at after passing under the Dutch submarine K-IX at its berth. The explosion sank Kuttabul and killed many of those aboard. Ban's midget submarine escaped the harbour.
The third midget, Number 21 from I-22 commandeered by Lieutenant Matsuo crept into the harbour and was sighted near the Heads, later unsuccessfully rammed about 11.00pm, and again sighted in Taylors Bay at 3.00am. The boat was attacked by depth charges from HMAS Seamist into the early morning of 1 June and crippled. When recovered with its two live torpedoes, the crew were found dead, having shot each other.
The Type A midget submarines were approximately 24 metres (80 feet) in length and carried two 18-inch torpedoes and could remain submerged for about 12 hours. On display at the Australian War Memorial, Canberra, is a composite craft made up of the remains of midget 21 and 14, while the remaining conning tower (from Number 21) is on display at the Garden Island Navy Heritage Centre, Sydney.
None of the five mother submarines survived wartime operations. I-22 and I-24 had launched their previous midget submarines during the Pearl Harbour attack of 1941.
Divers located the remains of Ban's and Ashibe's missing M24 midget submarine off Sydney's Northern Beaches in November 2006. The wreck site was provisionally declared an Historic Shipwreck under the Commonwealth Historic Shipwrecks Act 1976 on 24 November 2006, and with a no-entry Protected Zone of 500m radius on 1 December. The site and associated relics were also gazetted with an Interim Heritage Order under the NSW Heritage Act 1977 on 1 December. Penalties of up to $1.1 million dollars apply for breaches of this legislation.
