This diagram is based on Susumu Ito's sketch of his track over Sydney on 29 May (Peter Grose, 2007, p. 77. Illustration by Ian Faulkner. Click on the image to view a larger image.

There had been several early warning signs that something was being planned for Sydney. On 16 May, 30 miles east of Newcastle, there was a submarine attack (later identified as the I-29) on a Russian steamer called the Wellen. The ship was not badly damaged and managed to make it to Newcastle. I-29 was part of the midget submarine attack force.

There were reconnaissance flights over Sydney by the Japanese sea planes, on 23 May and 29 May, launched from the carrier submarines.

Phil Delhunty, an 18 year old on duty at the artillery battery at Georges Heights, on 29 May saw the seaplane, but mistakenly assumed it was from the USS Chicago.

‘As the plane got closer and closer I saw it was an aeroplane going by, a seaplane. I just thought: it’s off the Chicago or one of the American warships. You didn’t worry about it, nobody worried about it. Everybody thought it was American.’(Peter Grose,2007,p73)

A reproduction of the Japanese plan, showing the location of the mother submarines when they released their midget submarines. (Hugh Clarke and Takeo Yamashita, 1966, back cover)

There was also intelligence received on 26 May, from the New Zealand Naval Board that an enemy unit, probably a submarine was 700 miles east of Sydney. Further intelligence from the Board was received on 29 May, indicating the presence of an enemy unit 40 miles east of Sydney.

Finally, there was another midget submarine attack about 17 hours ahead of the Sydney attack, on Diego Suarez Harbour in Madagascar, which had only just been captured from the French.

Mother submarines from the Japanese Western Attack group launched three midget submarines into the harbour. Only one met with success — the midget launched from I-20. This fired a torpedo at the HMS Ramillies, tearing a hole in the ship. The battleship stayed afloat, despite severe damage. The submarine’s second torpedo had more immediate success, sinking the tanker British Loyalty.

Indicator reading registers Ha-14 entering the harbour. AWM 69/185

Unfortunately, the British Admiralty did not issue an alert of the attack to its allies, which might have prompted a review of Sydney Harbour’s defences.

There did not appear to be any extra vigilance in Sydney Harbour on the night of 31 May. The floodlights were on at Garden Island and the harbour was a hive of activity. Vessels were coming and going and ferries were doing their usual runs.

There was no hint that only seven miles east of Sydney, at about 5pm, three midget submarines were being released from three large I class Japanese submarines — Ha-21 (also known as M22) from submarine I-22; M24 (the midget’s Ha number is not known) from submarine I-24, and Ha-14 (also known as M27 or Midget B) from submarine I-27.

Ha-14 stuck in submarine net during recovery. Photographer: Percy Wilson. Courtesy: Helena Ackroyd Collection.

Indeed, the first sign of danger passed unnoticed at 8.01pm when the indicator loop recorded the inward crossing of the midget submarine, Ha-14 from I-27. The midget submarine had closely followed the Manly ferry into the harbour and was mistaken for the ferry.

Fifteen minutes later, a Maritime Services Board watchman, Jimmy Cargill, spied a suspicious object in the anti-torpedo net near the west gate. It was Ha-14, which had reversed into the net and was trapped. Cargill wasn’t sure if the object was a mine or a submarine, and took a second look with his colleague William Nangle, before reporting it to the patrol boat HMAS Yarroma, on duty at the western end of the net. The vessel was reluctant to come any closer in case the object was a mine. Instead, a stoker from the Yarroma was sent to accompany Mr Cargill to investigate. He confirmed the object was a submarine.

By this time, over an hour and a half had elapsed and the midget submarine’s desperate efforts to extricate itself from the net had failed. HMAS Lolita, which had been in position at the eastern end of the net approached to investigate. Confirming the presence of the submarine, Lolita launched her depth charges, but without success — they failed to detonate as they were set ‘too deep’. Within minutes, however, (at 10.37pm) a tremendous explosion rocked the harbour — the two crew members onboard Ha-14, Lieutenant Kenshi Chuman and Petty Officer Takeshi Ohmori, had fired their forward demolition charge, destroying the submarine and themselves.

Rear Admiral Muirhead-Gould. AWM007247

Meanwhile, at 9.48pm another inward crossing recorded on the indicator loop, again went unnoticed. This was M24 from I-24, piloted by Sub-Lieutenant Katsuhisa Ban and Petty Officer Mamoru Ashibe.

The Naval Officer in Charge of Sydney, Rear Admiral Muirhead-Gould had been hosting a dinner at his official residence ‘Tresco’, attended by Captain H. D Bode, commanding officer of the USS Chicago, as sketchy details began to emerge of events on the harbour. The official record of events (G Herman Gill’s official history Royal Australian Navy 1942–1945) suggests that at 10.20pm Captain Bode returned to his ship and at 10.27pm the order was given to close the harbour to outward shipping.

Some historians believe that in fact the dinner party did not conclude until after the Ha-14 was scuttled, and possibly not until after the USS Chicago opened fire on M24.

Only a short time later, at 10.50pm, Ensign Bruce Simonds aboard the USS Chicago, which was moored at Man at War Anchorage at Garden Island, spotted a periscope about 500 metres from the ship and opened fire with his .45 automatic pistol! The submarine was illuminated by the Chicago and then subjected to a torrent of shells from it, and the corvettes HMAS Whyalla and HMAS Geelong — much to the shock of passengers aboard a harbour ferry and other small craft in the vicinity. The M24 disappeared from sight soon after — no doubt submerging to escape attack.

Despite the potential danger to civilian craft, the ferries were allowed to continue running on the harbour. Rear Admiral Muirhead-Gould believed ‘the more boats that were moving about at high speed the better chance of keeping the submarines down ‘til daylight’.

USS Chicago, photo courtesy US Naval Historical Center

By this time, midget submarine Ha-21 from I-22  had also entered the heads, but had not crossed the indicator loop, so no time was recorded.

At 10.52pm a naval auxiliary boat, the HMAS Lauriana, which had heard the Ha-14 explosion, and was proceeding towards South Reef, spotted a conning tower ahead in the water. Being unarmed, it signalled the anti- submarine vessel, the HMAS Yandra, which was on patrol nearby. The Yandra tried to ram the submarine. After initially losing contact, it found the submarine again and dropped a pattern of six depth charges.

At 11.10pm the corvette HMAS Geelong, which was berthed at Garden Island fired at a suspicious object in line with Bradley’s Head. It is possible it was M24 checking its position in relation to the USS Chicago.

At 11.14pm all ships were instructed to be darkened. Some time later, the order was issued to turn the lights off at Garden Island off, but this proved easier said than done as Lieutenant Wilson, duty officer at Garden Island recounts in G Herman Gill’s official history Royal Australian Navy 1942–1945:

"I could not raise the dockyard by telephone so the Admiral sent me off on foot. Paul Revere had a more comfortable trip than I did. I ran at full speed across a rough and rocky dockyard road into the dock and through the work sheds. As I went through I shouted to all and sundry, “Get out fast, the port is under attack”.’ Some delay occurred finding the engineer responsible and with authority to put the lights out. When I found him he found it hard to believe, and spoke of the difficulty with hundreds of men in the dock, many below sea-level … [finally] he sent word to evacuate the dock and prepared to turn off the main switches. I ran back and it was only a few minutes after I reported that the torpedo exploded under Kuttabul."

Ban’s torpedoes were fired from the centre of the harbour.(Peter Grose, 2007, p. 140. Illustration by Ian Faulkner

About 12.30am, Sub-Lieutenant Ban in M24, near the centre of the harbour took aim at the USS Chicago moored at No. 2 buoy in Man-of-War Anchorage, near Garden Island and fired his torpedoes. The first torpedo passed astern of USS Chicago, went under the Dutch submarine K9, and slammed into the sea wall next to the HMAS Kuttabul, an accommodation vessel berthed on the north-eastern side of Garden Island. It ripped the Kuttabul apart and severely damaged the K9.

The second torpedo ran aground at Garden Island, but failed to detonate.

In the ensuing chaos the USS Perkins, USS Chicago and HMAS Whyalla made ready to quit the harbour. The channel patrol boat Toomaree was sent to the east boom gate and the Marlean and Sea Mist to the west gate. Steady Hour joined Lolita and Yarroma at the boom. There was now a concerted effort to find this and any other midget submarine in the harbour.

M24's unexploded torpedo on the bank at Garden Island. AWM305022

At 1.10am Rear Admiral Muirhead-Gould issued a message: Enemy submarine is present in the harbour and Kuttabul has been torpedoed.

At 1.58am the indicator loop recorded another crossing, identified later as the M24 leaving the harbour, some one-and-a-half hours after firing its torpedoes.

Sea Mist. Courtesy R T Andrew estate

An hour later, as the USS Chicago was leaving the harbour a periscope was spotted almost alongside. The ship signalled Garden Island: Submarine entering the harbour.

One minute later, an inward crossing was recorded on the indicator loop. This was Ha-21 making a late entry into the harbour, after recovering from the depth charge it received from Yandra earlier.

For the next two hours there were intermittent ‘sightings’ of midget submarines, but it was not until 5am that Ha-21 was discovered by the channel patrol boat, Sea Mist, in Taylors Bay, following reports of a suspicious object.

This rare picture is believed to show one of the depth charges being dropped in the harbour on the morning of 1 June 1942. It was taken by Norm Byrne RAN, who was aboard one of the navy auxiliary patrol boats. Courtesy Graeme Andrews collection.

Sea Mist confirmed the object as a submarine and dropped two depth charges on it. Both Yarroma and Steady Hour rushed to the scene and for the next three and a half hours proceed to drop depth charges. In the melee, it was thought there were two and possibly three submarines in the Bay. In fact, the Ha-21 had already been crippled and had sunk to the bottom of the harbour — its engine still running. The two crew members were dead — Lieutenant Matsuo is believed to have shot his colleague, Masao Tsuzuku, and then himself. They had been unable to detonate the submarine’s internal demolition charges.

For several hours there had been pandemonium on the harbour — sirens were sounding, searchlights, flares and tracer fire arced overhead. There were so many naval vessels swarming across the harbour, and such frequent explosions of depth charges and gunfire, it is a wonder there were no collisions or accidents.

Sydneysiders displayed a variety of reactions to the melee. Some blithely went about their business, others hurried to their nearest air raid shelter, while many rushed to the nearest vantage point to see what was happening on the harbour.

Kate Beecraft heard the explosions on the night of 31 May 1942

Kate Beecraft was in her early twenties and staying with her parents at Mosman while her husband was away in the war. She remembers the night of the midget submarine attack clearly. "We were at home when we heard the explosions on the harbour. I remember my father saying "I'm no navy man but I swear that noise was a torpedo". We didn’t do anything about it – there was so much going on during the war, there were always sirens going off."

Pamela Smith lived near the harbour

Ten-year-old Pamela Smith nee Stewart and her sister, at home in Cremorne Point, were hustled under the hall table by their mother. Pamela’s friend Louise Crisp, who lived nearby, slept through the drama and only learned about it at school the next day. When she asked her parents why they hadn’t told her it was because they ‘didn’t want to frighten me’.

There were several bizarre reports of events that night, including that the HMAS Marlean had been firing so wildly in Athol Bay there were fears for the safety of the animals in Taronga Zoo.

Louise Crisp lived near the harbour

Another eyewitness observed the patrol boat, the Kathleen Gillette, skippered by Jack Earl, rushing to the scene of the detonation of Ha-14 and hauling something — perhaps victims of the explosion — into their boat.  In fact, it was 20 kilogram gropers lying stunned on the surface of the water. There were certainly accounts in The Daily Telegraph of 2 June that dead fish were being washed up around the harbour.