Reconstructing the events of 31 May – 1 June 1942

At Sydney Harbour on the evening of Sunday 31 May 1942, the full moon was obscured by thick cloud cover. In the heavy swell, five huge Japanese I class submarines waited seven miles off the heads in preparation for their mission.

There were multiple fixed anti-submarine defences at the entrance to Sydney Harbour. Inner and outer loops recorded passing vessels, however on this night the outer indicator loops were out of action. An anti-torpedo boom was being constructed between George's Head on Middle Head, and Green Point on Inner South Head. The centre portion of the net was completed, but there were gaps at each end.  

Several large naval vessels were present in the harbour, including the American heavy cruiser, USS Chicago and the Australian cruiser HMAS Canberra. Nearby a former Sydney harbour ferry which had been requisitioned by the navy for accommodation, HMAS Kuttabul, which was lying alongside at the south-east corner of Garden Island.  

At about 4.30 pm the Japanese I class submarines released three midget submarines. The midget submarines passed through the heads into the harbour. Although the entrance of M27 was recorded by an indicator loop, due to the ferry and other marine traffic, its significance was not recognised.  

Approximately fifteen minutes later, a Maritime Services Board watchman named James Cargill sighted a suspicious object caught in the anti-torpedo net near the west gate. After investigations, it was reported to patrol boat Yarroma at 9.30 pm. After deciding that what was originally thought to be a magnetic mine was actually a submarine, permission was given to open fire.  

As this was happening, another inward crossing was recorded on the indicator loop. Again, it was interpreted as nothing special.

M24 was creating a stir in the harbour close to Chicago while M22 entered the Heads but did not reach the loop. It was sighted by Lauriana and Yandra who attacked with a pattern of six depth charges.  

At 10.27 pm, a warning instructed all ships in Sydney Harbour to take anti-submarine precautions and the port was closed to outward shipping. Ferries continued to run and this kept the submarines down until daylight. At 11.14 pm the instruction was given to darken the ships.

Approximately fifteen minutes later, M24 fired two torpedoes. One was a dud and did not explode. The second missed its target and hit the harbour bed below Kuttabul. Witnesses reported that they saw the whole vessel lift out of the water on impact before quickly sinking. The stern of the ferry sank immediately but the rest of the vessel took an hour to sink, leaving a portion of the top deck and the funnel above the waterline. The underwater explosion wrecked Kuttabul resulting in the deaths of 19 Australian  and 2 British sailors who were sleeping onboard. Survivors were pulled from the sinking vessel.

By now the harbour was on high alert with the patrol vessels slipped and sent on patrols with many periods of silence. Sea Mist, Yarroma and Steady Hour patrolled the west gate area.  

At approximately 5 am, Sea Mist investigated a suspicious object in Taylors Bay. Lieutenant Andrews from Sea Mist illuminated the object with an Aldis lamp, identified it as a submarine and made two depth charge attacks. Yarroma and Steady Hour came to the scene and more depth charges were dropped.  

The wreck of M22 lay on the harbour bed in Taylors Bay, battered by depth charge explosions, the torpedoes jammed in their tubes. Inside were the remains of the two crew members- Lieutenant Keiu Matsuo and Petty Officer Masao Tsuzuko.  

On 4 June 1942, the wreck was finally brought on shore. The occupants were found to have died by the result of self-inflicted gun shots to the head.  

The bodies of the four Japanese submariners recovered from the two submarines were buried with full naval honours. In 1943, the remains of the Japanese crews were exhumed, cremated and returned to Japan via diplomatic exchange. M24 disappeared from the harbour and was not located until 2006 off Bungan Heads, NSW.  

The attack on Sydney Harbour achieved little for the Japanese, but the midget submarine raid remains a potent symbol of the extent of Japanese operations against Australia during World War II.