M24 Japanese Midget Submarine wreck site is a heritage-listed former midget submarine and now archaeological site located in unincorporated waters off Sydney's Northern Beaches in New South Wales, Australia. The Ko-hyoteki-class midget submarine (also known as a Type A midget submarine) was designed by the Imperial Japanese Navy and built from 1941 to 1942 by Kure Naval Yard or Ourazaki Naval Yard. The site was added to the New South Wales State Heritage Register on 7 December 2007.
The wreck site is located below sea level and approximately from Bungan Head.
History
The Japanese midget submarine attack on Sydney Harbour was audacious and would have been even more spectacular had the primary military targets been successfully damaged. The attack showed the vulnerability of Australian ports like Sydney to long-range Japanese submarine patrols and the need for heightened security. Many Sydney-siders still recall the moments at night on 31 May – 1 June 1942 as the harbour lit up with depth charge explosions, tracer fire and criss-crossing harbour defence vessels. The explosion as a Japanese torpedo struck under the depot 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 Harbor on 7 December 1941, and the raid on Diego-Suarez in Madagascar on 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. A sixth submarine I-28 intended for the raid was sunk by the US submarine USS Tautog before it could deploy with a fourth midget. The five remaining mother submarines, which had left Chuuk Lagoon in the Pacific Ocean, arranged themselves in a semi-circle centred on Sydney Heads. A previous flight on 29 May by a reconnaissance aircraft launched from I-21 spotted potential targets inside the harbour. This Glen-type twin-float seaplane capsized when returning to its submarine and was scuttled. The remains of the seaplane have not been located.
At approximately 8pm on the Sunday evening, the first midget (number 14 from I-27) commanded by Sub Lieutenant Chuman, motored submerged into the harbour. Unfortunately for its crew, the boat became fouled inside the still incomplete anti-submarine boom net laid across the harbour between Georges Head and Green Point near Watsons Bay. Observed by surface craft near the Western Gate, the two-man Japanese crew decided to commit suicide when escape was hopeless. They fired the forward internal scuttling charge about 10:30pm and totally destroyed the fore end of the submarine. Remains of the wreck and its crew were later recovered.
Midget A (according to the Allied order of identification) from I-24, commanded by Sub Lieutenant Ban with Petty Officer Ashibe, next entered the harbour and followed a Manly ferry through the boom defences. The exact serial number of this submarine has not been ascertained, but it is now often referred to as M24. The submarine crossed the Indicator Loop system at about 9:48 pm. In a cat-and-mouse play, the submarine manoeuvred around the harbour and was sighted several times around 11:00 pm. Under fire from the heavy cruiser USS Chicago and several motor launches, the submarine successfully fired its two torpedoes about 12:30am from near Bradleys Head. Both missed Chicago – the prime target – one running onto Garden Island and failing to explode. The other struck underneath the ferry HMAS Kuttabul after passing under the Dutch submarine K-IX at its berth. The explosion sank Kuttabul and killed 21 of those aboard. Ban's midget submarine never made it back to the planned rendezvous point immediately south of Port Hacking.
The third midget, Number 21 from I-22 commandeered by Lieutenant Matsuo, crept into the harbour, was sighted near the Heads, and was depth-charged, then laid low before making a belated entry around 3:00am when Chicago was leaving port, and then variously sighted in the vicinity of Bradleys Head and the Taronga Zoo. The midget was definitely seen in Taylors Bay by 5:00 am. The boat was attacked with depth charges from HMAS Seamist, Steady Hour and HMAS Yarroma until 8:30 am on 1 June and crippled. When recovered with its two live torpedoes and unexploded scuttling charges, the crew were found dead, having committed suicide. The remains of Midget 14 and 21 were recovered from the harbour within a week and subjected to military interrogation.
The Type A midget submarines were approximately in length, carried two 18-inch torpedoes, and could remain submerged for about 12 hours. On display at the Australian War Memorial in Canberra is a composite craft made up of the remains of midget 14 and 21, while the remaining conning tower (from midget 21) is on display at the Royal Australian 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 Harbor attack of 1941.
M24 attack and escape The midget from I-24 (also referred to in the initial Allied reports as "Midget A", and colloquially as M24), commanded by Sub Lieutenant Katsuhisa Ban with Petty Officer Mamoru Ashibe, entered the harbour, crossing the indicator loop at 9:48 pm. It apparently followed a Manly ferry also through the Eastern Channel gate in the boom. The submarine ran up the harbour unobserved for an hour until at 10:52 pm when it was spotted near the Garden Island Naval Base, across from the Sydney central business district. This sighting occurred just twenty minutes after Chuman and Ohmori in Ha-14 blew themselves up in the antisubmarine nets at the other end of the harbour. Military authorities finally started to appreciate the scale of the problem.
M24's conning tower had been sighted by one of its prime targets, the American heavy cruiser USS Chicago, and soon by the Dockyard Motor Boat Nestor. Now in a position off Garden Island and apparently proceeding in a direction towards the Sydney Harbour Bridge, USS Chicago opened up with its five-inch guns and oerlikons. M24 was further attacked by HMAS Whyalla with its machine guns and HMAS Geelong from Bradleys Head. Recent research by historian Peter Grose indicates that one of Chicago's crew even emptied the magazine of his .45 automatic pistol at M24's conning tower.
The historical events have been well covered (e.g. Jenkins, 1992, Carruthers, 2006 and most recently by Grose, 2007), however it is still unclear why it took Ban and Ashibe another hour-and-a-half to run the from just west of Chicago to an attack position off its eastern-pointing stern.
Even allowing for the need to complete turns and circles, M24 had sufficient time to transit that limited distance, compared to the hour it had only taken to pass right up through the harbour. It is more surprising that Ban did not attempt to get into a more optimum firing position, immediately broadside of Chicago's hull. It now appears that Ban fired both his "fish" from a position astern of Chicago using the observed 60-degree deflection setting on his torpedoes – a tricky shot. This is possibly one reason why he missed. The unexplained time lapse and then apparently hurried attack may be explained by the fact that M24's crew rested on the seabed for some period prior to attacking their target, perhaps recovering from the earlier volley of fire.
It is confirmed that the submarine did successfully fire its two torpedoes about 12:30 am on 1 June from a position near the centre of the harbour abreast of Bradleys Head. The target was USS Chicago, still at its mooring at Man of War anchorage #2 and attempting to build steam to quit the harbour. The workers' lights on Garden Island were extinguished at about the same time Ban was taking his shots. Both missed Chicago, one running onto Garden Island and failing to explode amongst a pile of rope near the Gun Wharf. The other struck the island seawall under the ferry HMAS Kuttabul and exploded, sinking the vessel. The torpedo had first passed under the Dutch submarine K-IX at its berth alongside. K-IX was later wrecked in 1945 at Submarine Beach, Seal Rocks, and located in 1999 by the Heritage Branch via a remote magnetometer survey.
The sinking of Kuttabul killed 21 of those aboard, with ten others injured. Ban's midget submarine was never recovered by the mother submarines. What was later identified as an outer crossing on the harbour indicator loop at 01:58 am on 1 June has generally been regarded as M24 safely exiting Sydney Harbour. It was the only midget to successfully fire its two torpedoes and the only one of the three to escape. Again M24 took one-and-a-half hours to exit the harbour. This is compared to the hour that it took to enter and first be sighted in the vicinity of Chicago. M24 may have again rested inside the harbour for approximately half an hour after its failed attack.
Discovery In November 2006 Sydney-based recreational scuba divers from a private group, No Frills Divers, located the remains of Ban and Ashibe's missing M24 midget submarine off Sydney's Northern Beaches. The wreck was found approximately offshore from Bungan Head near Newport in over of water. Details of the discovery were broadcast on the Nine Network's 60 Minutes television program on 26 November 2006, and the announcement confirmed by the Minister for Planning, in conjunction with relevant Commonwealth government agencies on 1 December 2006.
Management A No-entry Protected Zone was declared around the fragile wreck site on 1 December 2006 by the Federal Minister for the Environment, under the Commonwealth Historic Shipwrecks Act 1976. The No Entry zone has a radius of , the centre of which is at the intersection of in Australian waters. Entry to the zone is restricted to researchers and site managers while the archaeological survey work is completed. Permits are issued by the Heritage Branch of the NSW Office of Environment & Heritage or the Federal Minister for the Environment, Canberra.
The wreck was also initially subject to an Interim Heritage Order under Section 24 of the NSW (State) Heritage Act 1977. On 7 December 2007, the M24 wreck site and a zone with a radius of was protected as an item of State Heritage significance on the New South Wales State Heritage Register. Penalties of up to AUS$1.1 million apply for disturbance of the wreck and surrounding debris field.
Description The Japanese Imperial Navy Type A midget submarines deployed at Sydney were approximately in length, of , and carried two torpedoes (Type 97, oxygen-driven, Kure Naval Yard). With a two-man crew, contemporary assessments suggested that they could remain submerged for about 12 hours in most operating circumstances. After this time the crew would be forced to replenish air and stamina levels. The submarines were of single-hull design using welded cold-rolled steel plates (MS44 quality, 5/16th inch), with a normal diving depth of up to and a collapse depth of . Powered by a electric motor, the boats could not recharge their initial battery capacity and therefore were totally reliant on the initial charge, careful management of the power reserve, and any technical breakdown or event that might impact the battery-operated electrical circuits. The design achieved an impressive surface speed, reportedly up to on the surface and submerged, far greater than other midget designs of World War II.