State heritage item data
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Name:
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M24 Japanese Midget Submarine wreck site
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Other names:
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Type A midget submarine
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Designer:
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Japanese Imperial Navy
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Builder:
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Kure Naval Yard or Ourazaki Naval Yard.
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Material types:
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Year construction started:
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1941
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Year construction completed:
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1942
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Modification dates:
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The date of consruction is not known although one of the midgets recovered from the Sydney Harbour raid was reported to have been built in 1942.
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Physical condition:
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The M24 is generally in reasonable condition however the external fabric has been damaged by commercial fishing trawling operations.
The wreck lies upright on sand and just under half buried in the sediment. It appears that the bow is slightly elevated as the lower torpedo tube is approximately a third filled at sand level. Both tubes are empty of their torpedoes confirming the identification of the vessel as M24, the only midget to successfully fire its two torpedoes. The upper tube has been torn off the vessel back to a substantial bulkhead and lies almost totally buried in sand adjacent to the bow on the port quarter.
At the stern, sand levels lie at the centreline of the propeller boss (missing). Both contra-rotating propellers are visible, although all exposed rudders, stabilisers and the protective cage around the propellers have been removed by fishing nets. Just forward of the stern, the topside manhole that gave access to the motor room appears lost to corrosion, providing a minor cavity in the hull plating.
The internal hull aft of the control room is over half filled with sand as evidenced through several significant openings in the pressure hull. These openings extend around the hull immediately aft of the rear control room bulkhead and beyond the conning tower area (see below). They extend from sand level to the roof, with corrosion processes resulting in plate loss back to internal transverse frames. The openings allow water movements through this aft battery room and tend to 'self-flush' this major compartment, keeping sand levels down. Several fittings and fixtures that adorn the aft battery room are visible through these openings (discussed in detail below)
Significantly, the control room compartment is partly filled with sand to under the original internal casing 'roof'. This sand has apparently entered the space as a result of significant damage to the upper conning tower structure and the aft battery room openings, mentioned above. Externally, all plating that comprised the conning tower has been removed from the hull, including the forward access 'chute' into the control room. This once formed part of the pressure hull and its removal has formed an artificial opening into the main hull atop the submarine. Only the pressure dome and periscope standard of the aft portion of the conning tower survives intact, however, the damage has created an opening of approximately fifty (50) centimetres in diameter.
Drift sand has probably entered the control room space partly through this opening and apparently to the same depth as observed in the aft battery room. When the No Frills Divers video footage of the wreck was first examined, there was an indication that the rear bulkhead door into the control room was closed. This led to speculation that both fore and aft doors were probably closed to enable sand accumulation and retention within the control room space. However, the current surveys have suggested that the aft door to the control room is in fact open, though significantly sanded up. It is likely that the forward control room bulkhead door is closed to assist sand build up. If future examination shows this is not the case, the forward battery room and perhaps the torpedo room, must also have significant introduced sand deposits.
Inside the periscope well, the upper portion of the periscope tube is visible transiting into the control room sand deposit. The periscope does not extend externally beyond the periscope standard, suggesting that it has retracted into the periscope well built into the floor of the control room. At no point could the upper lens of the periscope be sighted within the outside opening of the periscope standard.
Around the internal upper 'walls' of the control room are several gauges and levers that comprise part of the operating controls of the submarine. Of particular interest are the 'steps' built into the forward face of the periscope well that allowed crew egress and ingress, and the clearly visible retractable two-step crew ladder hinged at the weld join of the periscope dome and the 'ceiling' of the pressure hull. This ladder is still in its upright or 'stowed' position, once within the cavity of the 1.5 metre-deep access chute, now lost. This is the firmest indication that the crew of M24 are most probably still within the submarine hull. To exit the craft, Ban and Ashibe would have had to pull down this hinged ladder to climb up and out of the Control Room.
The original 'signature' of the external conning tower plating is clearly visible on the upper surfaces of the wreck, marked by the angle iron framework where it was attached to the casing.
Some elements of the conning tower still survive in the debris field that surrounds the wreck. Almost incredibly, the water-tight hatch that once sealed the access chute lies beside the conning tower on sand to port. Once upright, the lid has been turned over by divers to reveal its underside and locking mechanism, which appears to be in the 'locked' position. While there is no sign of the significant access chute itself (part of the original pressure hull), the harbour net cutter that once adorned the forward conning tower, with its distinctive 'teeth', lies separated on the sand, also on the port side, slightly abaft the conning tower. Resting against the submarine hull, its 'wishbone' attachment frame is clearly visible.
The main hull forward is mostly intact, and unlike the stern, reveals no visual access points into either the forward battery room or torpedo room. Apart from some abrasion to the upper hull surfaces caused by fishing nets, and perhaps some modern impact by an anchor or some other foreign object, there is no significant damage to the casing. Hence it is impossible to postulate the internal condition of their internal spaces, including the presence, or otherwise, of sand levels or other relics.
Like the conning tower, the forward bow area has witnessed significant physical damage. As noted, the upper of two torpedo tubes has been almost half torn off the hull and now lies in the sand to port. The main bulkhead (at frame 7) is clearly exposed, while the lower tube is completely intact to the bow. Running along the forward centreline of the casing, the original hydraulic line that extended to the bow torpedo cap release has been torn off and lies across the hull to port. Most of the front end of the submarine is still concealed by entrapped fishing nets that make interpretation difficult. What is clear is that the protective cage around the torpedo tubes has been removed from the hull, including the forward net cutting gear and serrated jump cable that passed from here back to the conning tower, and aft. It is possible that some of these elements might be detected with a fuller examination of the major debris field that extends out from the bow of the wreck for some one-hundred meters on sand.
The initial archaeological survey taskings have indicated that no scuttling charges have been fired by the crew, nor that there is any obvious battle damage to the hull.
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Physical description:
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The Japanese Imperial Navy Type A midget submarines deployed at Sydney were approximately 24 metres in length (80.5 feet), of 46-7 tons, and carried two 18-inch 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 normal operating circumstances. After this time the crew would be forced to replenish air and stamina levels. The submarines were of single (pressure) hull design using all welded 8mm cold rolled steel plates (MS44 quality 5/16th inch), with a normal diving depth of up to 100 metres and a collapse depth of 200 metres . Powered by a 600 horsepower 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 susceptibilities of any technical breakdowns or events that might impact battery operation electrical circuits. The design achieved an impressive surface speed reportedly up to 24 knots on the surface and 19 knots submerged far greater than other midget designs of World War two.
The Sydney boats had some design modifications to those captured at Pearl Harbour, with a slightly wider hull at 6-feet (1.8 metres). The vessels were electrically powered by 208 lead acid wet cell batteries (72 forward and 136 aft), and had three main sections jointed 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 After Section (containing the motor, propeller shaft and gearing). Other improvements included an improved gyro compass, access way hatch on underside to permit crew transfers at sea, and an eye piece fitted into the sides 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.
The type was designed in Japan during the 1930's with two experimental boats Ha-1 and Ha-2 built as early as 1936. The building program was concentrated from 1938 onwards where 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 were known by many secret names, such as sheaths, 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, for example, some quoting 59 Type A's 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.
Japanese midget submarines had there 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 same and therefore their identification number was often different to the I-class submarine carrier.
DATA
Weight: 46 tons
Length: 23.9 meters (78 feet)
Forward section: 17 feet
Midship section: 34 feet 11 inches
After section: 22 feet 4 inches
Nose guard: 3 feet
Diameter amidships: 6 feet
Height of conning tower: 4 feet 6 inches with additional guard structure 15 inches high. (Clarke and Yamashita 1966; To Sydney By Stealth)
Beam: 1.8 meters (6 feet)
Electrically propelled: 1 x 600 hp
Maximum surface speed:23 knots
Maximum submerged speed:19 knots
Propulsion:1 shaft but fitted with contra-rotating propellers.
Range: About 15 miles at full speed or 80 miles at 2 knots, and without any self-recharging capability for the batteries. Each boat carried 2 x 17.7 w (457mm.) Model 2 torpedoes with a range of 3000 meters at 40 knots.
Crew:2
Equipment: Radio set with a raiseable mast. Electrically raised periscope. Echo sounder.
(Source: The Naval Historical Society of Australia Inc. Monograph 165. John C. Date, 2001)
Torpedoes:18 inches, 5 feet 8 inch-long warhead and 17.5 inches in diameter (Clarke and Yamashita 1966; To Sydney By Stealth).
Crew of M24
Sub Lt. Katsuhisa Ban
Petty Officer Mamori Ashibe
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Historical notes:
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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 ports like Sydney, Australia, 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 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. A sixth intended submarine I-28 was sunk by the US submarine USS Tautog before it could deploy with a fourth midget. The five remaining mother-submarines, which had left Truk (Chuuk) Lagoon in the Pacific, arranged themselves in a semi-circle centred on Sydney Heads. 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 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 Watson's 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 (or M-24), commanded by Sub Lieutenant Ban with Petty Officer Marmoru 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. 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 under 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 was never recovered. Many theories were advanced for its probably resting-place, with wartime confirmation that the crew 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 and was sighted near the Heads and depth charged, 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 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 in the morning of 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 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 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.
Details of 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 Sydney's central business district. This sighting occurred just twenty (20) minutes after Chuman and Ohmori in Ha-14 blew themselves up in the harbour 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 200 yards off Garden Island and apparently proceeding in a direction towards Sydney's Harbour Bridge, USS Chicago opened up with its five-inch guns and oerlikons. M24 was further attacked by Whyalla with its machine guns and Geelong from Bradleys Head. Recent research by historian Peter Grose indicates that even one of Chicago's crew emptied the clip of his .45 automatic pistol at M24's conning tower!
The historical events have been well covered (eg 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 mile 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 part of the explanation why he missed. The unexplained time lapse and then apparent hurried attack requires some additional thought though. For some period M24's crew rested on the seabed prior to attacking their target, perhaps recovering from the 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 nearing the centre of the harbour abreast of Bradley's 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 (later wrecked in 1945 at Submarine Beach, Seal Rocks, NSW, and relocated by the Heritage Branch via a remote magnetometer survey in 1999 ).
The sinking of Kuttabul killed twenty-one 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 some one and a half hours to leave from its attack position and 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
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 in November 2006. The wreck was found some three miles offshore from Bungan Head near Newport in over fifty metres of water. Details of the discovery were aired on Channel 9's "Sixty Minutes" 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 is bounded by an imaginary line forming a circle with a radius of 500 metres the centre of which is at the intersection of the parallel 33 40' 21" South latitude with the meridian 151 22' 58" East longitude as consists of Australian waters. The M24 wreck site is encapsulated within this protective zone. 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, Office of Environmnet & Heritage, Sydney, 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 500-metre radius zone was protected as an item of State heritage significance on the State Heritage Register (SHR). Penalties of up to $AUS1.1 million apply for disturbance of the wreck and surrounding debris field. The Heritage Branch has coordination of the survey and assessment of the wreck site and is developing management options, survey reports and interpretative information that will be progressively added to this site.
See also:
Attorney Generals Department (Commonwealth)
http://www.ag.gov.au/portal/govgazonline.nsf
Department of Environment and Water Resources (Commonwealth):
http://www.environment.gov.au/index.html
Heritage Branch, NSW Department of Planning
http://www.heritage.nsw.gov.au
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Statement of significance:
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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 being recovered). The site is the only in situ identified cultural relic surviving of the attack on Sydney Harbour in 1942. A complacent Sydney population awoke to the realisties of war 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 unique underwater contexts. Remains of a further six are retained as static museum or outdoor display exhibits. The archaeological site is therefore of considerable importance in the comparative analysis of midget submarines wrecks discovered world-wide. 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.
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Current use:
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Restricted site for detailed archaeological survey
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Former use:
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Midget submarine for offensive attacks on shipping and port facilities.
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Group name:
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Group name 2:
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Transport - Water
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Type name:
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Archaeological-Maritime
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Category name:
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Naval vessel
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Circa flag:
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Yes
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Further information:
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The Heritage Branch, Office of Environment and Heritage, is the lead agency in the management of the Historic Shipwreck under the NSW Heritage Act 1977 and Commonwealth Historic Shipwrecks Act 1976 provisions. The agency has been leading the archaeological survey of the wreck site since its discovery by recreational SCUBA divers, No Frills Divers, in November 2006.
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management:
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