M24 Japanese Midget Submarine wreck site

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.[1]

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.[1]

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.[1]

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.[1]

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 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.[1]

The Type A midget submarines were approximately 24 metres (79 ft) 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 Naval Heritage Centre, Garden Island, 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.[1]

The Japanese Imperial Navy Type A midget submarines deployed at Sydney were approximately 24 metres (79 ft) in length, of 46–47 short tons (42–43 t), and carried two 46-centimetre (18 in) 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 8 millimetres (0.31 in) cold-rolled steel plates (MS44 quality, 5/16th inch), with a normal diving depth of up to 100 metres (330 ft) and a collapse depth of 200 metres (660 ft). Powered by a 450 kilowatts (600 hp) 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 24 knots (44 km/h) on the surface and 19 knots (35 km/h) submerged, far greater than other midget designs of World War II.[1]

The Sydney boats had some design modifications compared to those captured at Pearl Harbour, with a slightly wider hull at 1.8-metre (6 ft). The vessels were electrically powered by 208 lead-acid wet-cell batteries (72 forward and 136 aft), and had three main sections joined by internal flanges, bolted together. These comprised the Forward Section (containing the torpedo tubes), the Central Section (containing the Forward Battery Room, Conning Tower and Aft Battery Room), and the Aft Section (containing the motor, propeller shaft and gearing). Other improvements included an improved gyro compass, an accessway hatch on the underside to permit crew transfers at sea, and an eyepiece fitted into the side of the Conning Tower. Other fundamental additions included the fitting of an improved nose guard and propeller guard, and the distinctive net cutters at bow and atop the Conning Tower.[1]

The type was designed in Japan during the 1930s, with two experimental boats Ha-1 and Ha-2 built as early as 1936. The building program accelerated from 1938 onwards, when some fifty Type A boats were built at Ourazaki and Kure naval yards, the majority between 1940–2 (number sequence Ha-3 to Ha-52). The class was known by many secret names, the most commonly-ascribed being "Ko-Hyoteki" or "Target A", with the Sydney boats being an improved version, Type A Kai 1 (improved version 1). Records of production are limited and total production numbers are variously reported, with some for example quoting 59 Type As produced. The Japanese designed several variants to the Type A midget during the war, including the important Hei Gata (Type C) and the most prolific Koryu (Type D), fitted with generators to allow battery recharge and additional crew.[1]

Japanese midget submarines had their own numeric designation based on production sequences (a "Ha" number reference is often used today). They could be deployed on any of the mother carrier submarines fitted for them and therefore their identification number was often different to the I-class submarine carrier.[1]

The M24 is of heritage significance to Australia and Japan, and is the only Japanese midget submarine wreck located in Australian waters (the remains of two others from the Sydney attack having been recovered). The site is the only in situ-identified cultural relic of the attack on Sydney Harbour in 1942. A complacent Sydney population awoke to the realities of war due to this attack, and the event is strongly remembered today through the wider community. The M24 wreck is representative of Japanese submarine operations off Australia's eastern seaboard during the war and a direct physical reminder of the conflict at Sydney. Internationally, it represents one of only a handful of Japanese midget submarine wreck sites located in their underwater contexts. Remains of a further six are retained as museum or outdoor exhibits. The archaeological site is therefore of considerable importance in the comparative analysis of midget submarines wrecks discovered worldwide. The site also has the ability to contribute generally to studies of submarines as a specialised class of archaeological site type. Only limited archival information related to these vessels survives and therefore the archaeological record is of added importance. In regard to the three submarines that attacked Sydney Harbour, M24 is the only one retained in its original battle context and undisturbed, apart from the obvious effects of net entrapment and corrosion activity.[1]

M24 Japanese Midget Submarine wreck site was listed on the New South Wales State Heritage Register on 7 December 2007, having satisfied the following criteria.[1]

The place is important in demonstrating the course, or pattern, of cultural or natural history in New South Wales.

The Japanese submarine attack on Sydney Harbour was part of a series of pivotal aggressive moves by Japan during the early stages of World War II, and closely followed the attack at Pearl Harbour, Hawai'i just six months prior. The sizeable Japanese naval force of eight submarines comprised the first active attack on Sydney in its history. While the raid was militarily of limited success, it highlighted the vulnerability of important Allied naval station and repair facilities, and ships, to long-range submarine attack. The loss of 21 naval ratings aboard the depot ship HMAS Kuttabul to one of M24's torpedoes is still remembered by the navy through the annual HMAS Kuttabul Memorial Service held at Garden Island Naval Base. The raid awoke a complacent Sydney population to the realities of war. The sale of artefacts from and regional tours of one of the captured midget submarines played a major role in raising awareness and in generating financial contributions to the War Bonds Scheme.[1]

The place has a strong or special association with a person, or group of persons, of importance of cultural or natural history of New South Wales's history.

The M24 was the only Japanese midget submarine to successfully enter Sydney Harbour, fire its torpedoes and escape. The other two boats, Ha-14 and Ha-21 were disabled in the conflict and later recovered. The final fate of M24 and its brave crew of Sub Lieutenant Ban and Petty Officer Ashibe became one of Australia's enduring naval mysteries until the site was discovered by recreational divers in November 2006.[1]

The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales.

The M24 wreck site provides an opportunity to document and analyse the form, fit-out and construction of a Japanese Type A midget submarine from World War II. The archaeological record is of added importance with a limited number of archival references relative to this type of vessel. Aesthetically the M24 represents a rare opportunity to see a historically-significant submarine wreck site in its underwater setting, providing scope for world-class photographic documentation and potential controlled visitation by the recreational community.[1]

The place has a strong or special association with a particular community or cultural group in New South Wales for social, cultural or spiritual reasons.

The attack awoke a relatively complacent Sydney wartime population to the realities of the present conflict. The raid, which included eight Japanese submarines and over 500 Japanese Imperial Navy sailors, was the only direct attack on Sydney in its history. The event is well-remembered by the population nationally. In Sydney, the event is particularly closely felt because so much of the present population were witnesses to the raid. Such was the impact on Sydney that many school children and even whole families temporarily relocated from Sydney to places such as the Blue Mountains and beyond, fearing another attack, more coastal shelling, or even invasion.[1]

The place has potential to yield information that will contribute to an understanding of the cultural or natural history of New South Wales.

The M24 is the largest surviving archaeological relic in situ from the Japanese attack on Sydney Harbour on 31 May 1942. The M24 hull and associated relics have been retained in their archaeological context and unaltered, apart from damage by fishing net hook-ups. The site and artefacts have the potential to contribute to technical studies of the construction, fit-out and materials used in Japanese midget submarines of World War II. The site has potential to contribute to studies of corrosion activity of steel shipwrecks in coastal marine environments, and the effects of localised environmental factors. The archaeological site is of added value to researchers as a storehouse of information that is not available through the scant archival records that survive for this class of vessel.[1]

The place possesses uncommon, rare or endangered aspects of the cultural or natural history of New South Wales.

The M24 represents the only Type A Imperial Japanese midget submarine located in its original underwater context in Australian territorial waters. The partial remains of only two other examples survive in museum displays within Australia, which have been substantially stripped of fittings and fixtures. The M24 is one of five midget submarine wrecks located underwater internationally and six on museum display.[1]

The place is important in demonstrating the principal characteristics of a class of cultural or natural places/environments in New South Wales.

The wreck site is a representative example of the Type A Japanese midget submarines deployed in the first stages of World War II. The type saw action throughout the war but was superseded by later variants. As an example of the boats deployed in major war theatres such as Pearl Harbour, Sydney and Madagascar, the M24 wreck has the potential to document the main attributes of the class and various design additions.[1]

• Attack on Sydney Harbour
• Military history of Australia during World War II

• Attorney Generals Department (Commonwealth)
• Department of Environment and Water Resources (Commonwealth)
• Heritage Branch, NSW Department of Planning