Managing a Japanese Midget Submarine M24
Managing an M24
Tim, what is so important about the M24?
The M24 is a rare maritime heritage site that is of state, national and international significance. M24 is the only Japanese Type A ‘Ko Hyoteki’ Imperial Japanese Navy (IJN) midget submarine out of some 7,500 shipwrecks in Australian waters. It is the last significant item associated with the daring 1942 submarine attack on Australia’s principal naval port and largest capital city, still in situ. When found by No Frills Divers in 2006, M24 joined only a handful of Japanese midget submarines located underwater in the world. The M24s story is linked to the infamous Pearl Harbour attack of 1941, just six months before. The carrier submarine I-24 which launched M24 at Sydney had previously launched a midget submarine in that attack. M24, along with its two sisters deployed at Sydney had several design modifications made after an assessment of their capabilities following Pearl Harbour.
What can the wreck site tell us that we don’t already know from historic records?
Due to wartime secrecy and the effects of heavy bombing across Japan by war’s end, not much survives in Japanese archives about the development of the craft, their capabilities, or the crews that operated them. Much of what we know about the ultra top secret submarines comes from American and Australian assessments of a captured submarine from the Pearl Harbour raid, and the two captured from Sydney Harbour following that attack. But those records too are limited while those midget submarines on museum display (such as the composite of Ha14 and Ha21 in the Australian War Memorial), have been heavily stripped out of machinery and other fittings during the war, and as souvenirs to help fund War Bonds schemes. They provide useful objects for studying how midget submarines were made but none is in complete form. That is why sites like M24 are so important they are largely intact and potentially contain within their hulls all associated objects carried by the crews into battle.
What can M24 tell us of the Sydney midget submarine attack on the night of 31 May 1942?
The M24 wreck site gives us clues to the battle plan of the Japanese task force that comprised five large (110 metre long) carrier submarines and three midget submarines. M24 was the only midget that successfully entered the defended harbour, fired its torpedoes at a target (the American heavy cruiser USS Chicago), and escaped. By leaving the harbour we can see that its crew - Katsuhisa Ban (23) and Mamoru Ashibe (24,) were intending to rendezvous with its carrier submarine. This was in fact the order of the Navy’s Commander in Chief, Admiral Yamamoto. When the No Frills Divers found the wreck off Bungan Head, Newport, on Sydney’s Northern Beaches, it was at first a surprise. Limited documents suggested they were to rendezvous off Sydney’s southern Royal National Park. The Heritage Branch revisited the charts from one of the captured Sydney midgets and confirmed that M24 was actually on a predetermined track back to its carrier submarine I24 off Broken Bay. This had been an earlier agreed rendezvous location. So, M24s final resting place is quite historic. For some reason it only made it half way along this track, having made some 10 miles after leaving Sydney Harbour at about 2am on the morning of 1 June 1942.
There are a number of scenarios but the most likely ones are that the submarine just ran out of its battery power, the crew ran out of air, or they were overtaken by some other event such as toxic fumes from the batteries. Perhaps the submarine had been partially disabled. The Heritage Branch believes that a possible scenario has the submarine reaching Newport by first light on 1 June 1942. They would have been forced to keep submerged to evade detection by naval and air force searches, but that would have meant at least another twelve hours sitting on the bottom before they could signal to their mother craft to be collected. Perhaps this was just physically beyond their endurance. Did Ban and Ashibe choose to shoot themselves with the one service pistol? Just as their colleagues in Ha21 were forced to do when depth charged inside the harbour?
Why is the recent archaeological survey that features on Channel Seven’s Sunday Night program so important?
The Heritage Branch has led many archaeological surveys at the site since its discovery six years ago and we now know a lot about the external appearance and condition of the wreck site. We know that it has been damaged in decades past by commercial fishing trawl nets, with much of the bow and most of the conning tower and stern propeller cage torn off. What we don’t know much about is the internal condition of the submarine - what was the state of its two internal watertight doors? What’s the condition of the internal surfaces and the rate of corrosion? Can we find any evidence of the crew and their final actions?
Some of these questions we may never answer due to a build up of sand inside the hull. Much of the internal fittings are now buried, together with the hundreds of small relics that would be contained inside, like the crews’ personal effects, food containers, bottles of soda water, navigational equipment, etc.
The current inspection of the control room space and aft battery room (through openings formed in the hull), now gives us much clearer picture of the visible portions of these spaces. Footage obtained inside the control room where the crew lived and worked is revealed, with key elements such as the periscope documented, together with other fittings. The state of the two-rung crew ladder that gave access into and out of the hull is seen. Up in the stowed position, it is an important clue that the brave crew never escaped. They would have had to pull the ladder down to exit the conning tower ‘fin’. We may never know their final moments and actions, or where they lie entombed within the wreck due to current sand levels. However, every interrogation of M24 gives us another insight into this amazing story of wartime daring, drama, and sadness, right on Sydney’s doorstep. The M24 is a critical link to the story that overtook Sydney and the nation during the darkesy days of World War Two.
Protection
The M24 archaeological site is protected by the Heritage Act 1977 (NSW) and Commonwealth Historic Shipwrecks Act 1976. Penalties up to $1.1M apply for damage to the site. A no entry 500 metre radius Protected Zone is gazetted around the site which is covered by a high-tech security system with back-to-base alarms and real-time video monitoring.
For more information on M24, visit the Heritage Branch’s M24 web exhibition, managing the Missing M24 midget submarine.
-Responses by M24 Project Manager Tim Smith: Deputy Director, Heritage Branch, Office of Environment and Heritage.
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