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46 Tons (Surfaced)
47 Tons (Submerged)
78.5' x 6' x 10.2'
2 x Type 97 torpedo
140kg scuttling charge
Arnold Nov 12, 2006
Allen December 21, 2017
|Commander Lt(jg) Katsuhisa Ban (KIA)
Crew PO1c Mamoru Ashibe (KIA)
Sunk June 1, 1942 at approximately 2:00am
Built by Ōurasaki Naval Armory as a Kō-hyōteki kō-gata submarine (Type A midget submarine). Delivered to the Imperial Japanese Navy (IJN) as HA-24 Type A Midget Submarine (M24).Assigned to captain Lt(jg) Katsuhisa Ban and crew member PO1c Mamoru Ashibe.
This midget submarine was transported to Truk. Originally, M24 was intended to go aboard Japanese submarine I-28. Instead, on May 20, 1942 loaded onto the deck of Japanese submarine I-24 with her crew embarked aboard the submarine and departs the same day proceeding southward to Sydney on a mission to mount a midget submarine to attack Allied warships in Sydney Harbor.
On May 31, 1942 at 5:40pm I-24 roughly 7.5 miles east of Sydney launched this midget submarine on a mission to attack Allied warships in Sydney Harbor. A total of three midget submarines participated in the attack: M24 (this submarine) plus M22 (launched by I-22) and M27 (launched by I-27).
At 9:50pm, M24 crossed the indicator loop at the entrance to Sydney Harbor unnoticed. At 10:07pm, all vessels in Sydney Harbor were alerted of the presence of an enemy submarine. At 10:50pm M24 was spotted by the crew of the USS Chicago CA-29 which opened fire along with two other Australian ships. This submarine evades them and waited for an hour and a half then resumed her mission.
On June 1, 1942 at 12:30am, M24 fires both torpedoes at USS Chicago CA-29, but both missed. One ran aground without exploding. The other hit the sea wall at Garden Island, and the explosion sink HMAS Kuttabul moored nearby and killed 21 aboard and damaged Hr. Ms. K IX.
At 2:00am, the indicator loop at the entrance of Sydney Harbor registers a possible submarine crossing, likely the passing of M24. This submarine never reached the rendezvous point and was presumed lost. In fact, this submarine managed to exit Sydney Harbor then sank or was scuttled for unknown reasons. Until the submarine was located in 2006, its precise fate was unknown.
On November 12, 2006 this submarine was discovered on a flat sandy bottom at a depth of 54m / 177' by a dive team including Greg Kearns, Dave Arnold, Alan Simon, Paul Baggott, Ton Hay, Dave Muir, and Phil Hendrie. The submarine was confirmed by Australian Naval Historian Shane Moore. Neither torpedo was aboard the submarine, confirm both had fired both during the attack. The bow section is damaged and the net cutter is laying on the bottom.
On November 25, 2006, Australian Defense Minister Brendan Nelson moved to protected the submarine an historic shipwreck under the Australian Historic Shipwrecks Act (1976) with a 500m protected zone around it with monitoring the restricted area with sonar alarms and underwater cameras.
In late May 2007, Australian authorities decided not to salvage the submarine or the remains of the crew. Divers from the Royal Australian Navy did recovered sand from the sea floor nearby to present to the families of the two crew members.
In recent years, limited SCUBA diving has been allowed at the site with permission. During December 2017, divers Liam Allen, Richard Nicholls, Matt Small and Stephen Ho dove and documented the submarine.
This submarine is also referred to as HA-24b or No. 24b as the second midget submarine launched by I-24. Other sources list PO1c Mamoru Ashibe with the rank of Ensign incorrectly.
RAN Japanese Midget Submarine Attack on Sydney Harbour by John Perryman
Sydney Midget Submarine Discovery by Kearns, Arnold, Simon, Baggott, Hay, Muir, and Hendrie
ABC "Naval historian says wreck is WWII sub" November 26, 2006 via Wayback Machine February 25, 2007
ABC "Nelson moves to protect WWII sub wreck" November 27, 2016 via Wayback Machine February 24, 2008
Australian 60 Minutes - November 26, 2006
BBC News "Japan WWII Sailors Stay in Wreck" May 22, 2007
NSW Environment & Heritage - M24 - Managing The Missing Midget Sub last updated October 24, 2012
Thanks to Sydney Midget Submarine Discovery Team, Dave Arnold, Tim Smith and Liam Allen for additional information
May 31-June 1, 1942
View on Google Earth
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