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Introduction

The threat of a Japanese invasion was thought to be imminent for Australia after the fall of Singapore. Darwin had been crippled by a series of Japanese air raids. In May 1942, Japanese Midget submarines were spotted in Sydney Harbour, posing a direct threat of attack or invasion.

The presence of Japanese submarines in Sydney Harbour caused alarm in the residents of Sydney and the Australian defence forces. Again, Australia was unprepared to defend against Japanese incursions.

Japanese intentions and Sydney unsuspecting

There were 5 I-class submarines in the vicinity of Australia under the command of Captain Hankru Sasaki. These full-sized submarines carried 3 Type-A Midget submarines. The Midget submarines were 30 metres long, battery powered and crewed by two men.

There were two planes attached to the Midget submarines that entered Sydney Harbour. These planes were used for flights over Sydney Harbour, one undetected on 23 May, and the other on 30 May.

The Japanese preferred to use Midget submarines during the war. They were used at Pearl Harbor and Madagascar before Sydney. While it was difficult to manoeuvre a Midget submarine, they were small enough to enter a harbour undetected and could strike a decisive blow against Allied vessels. The Japanese built 500 of these submarines during World War II. See image 1

On 16 May 1942, the Russian ship Wellen was attacked by Japanese naval vessels 56 kilometres from Newcastle, New South Wales. On 23 May, the New Zealand Naval Board issued a warning that there was a group of submarines 65 kilometres from Sydney. The warning was officially issued on 30 May.

Despite the warnings, Sydney was not prepared for, and took few precautions against, an attack. Australia was celebrating victory in the Coral Sea against the Japanese navy. During the weekend of the Midget submarine incursions, Australian and American soldiers were celebrating. See image 2

The harbour defences were not complete. The anti-submarine net at Georges Head had not been completed. The ships which were supposed to be patrolling the harbour were used as pleasure boats. The naval vessels stationed in Sydney Harbour were crowded together and were silhouetted and identifiable against the bright lights of the city.

30 May 1942

At 2.47 am on the Saturday morning, pilot Susumu Ito flew over North Head and Sydney Harbour, following a Manly ferry. The plane flew close to the ground and used navigation lights only, dimmer than the usual aircraft lights. An anti-aircraft battery at Middle Head spotted the Japanese plane but mistook it for an American Curtis Falcon float plane and raised no alarm.

There were no guns or identification on the plane - it was performing reconnaissance only. The Japanese plane flew around Garden Island twice, noting the position of American tankers and various naval vessels, such as the USS Chicago. An anti-submarine net was being constructed in Sydney Harbour but had not been completed.
 
As the Japanese reconnaissance plane returned to the aircraft carrier, it crashed into the ocean. Nevertheless, the Japanese were able to retrieve the pilot and his information, which proved to be critical for the submarine attack the next night.

31 May 1942

At 8 pm on Sunday, three Japanese Midget submarines detached from the larger submarine carriers. Armed with two torpedoes each, the Midget submarines ventured into Sydney Harbour. The Japanese submariners intended to fire a torpedo at one of the many ships docked in Sydney Harbour to set off a chain reaction that would destroy all the ships in the harbour.

The first Midget submarine to enter the harbour was M 27 commanded by Lieutenant Jahai Chuma. The submarine closely followed the Manly ferry but became tangled in the netting of the boom net.

Chuma attempted to untangle the submarine by using sawtooth metal cutters. This only tangled the submarine further. By 8.30 pm he had attracted the attention of the watchman for the Maritime Service Board, James Cargill. He rowed across in a boat and discovered the Japanese submarine.
 
Surprised, Cargill radioed naval headquarters. It took him two hours to convince the navy that there was a Japanese Midget submarine caught in the boom net.
 
Chuma realised he had been detected and at 10.27 pm detonated his submarine, killing himself.
At 10.36 pm, the Commander of New South Wales Coastal and Harbour Defences, Rear Admiral Muirhead-Gould issued an official alarm.

A flurry of Allied patrol vessels and warships rushed to the defence of the harbour, but found no other submarines.

At 9.48 pm the second Japanese Midget submarine, M24, entered the harbour under the command of Katahuisa Ban. The submarine entered the harbour near the shoreline of Garden Island. The M24 was not submerged and was spotted by sailors on the USS Chicago at 10.30 pm. The Chicago shot at it. The submarine then almost crashed into the Nestor.

After another 10 minutes, the M24 was fired upon again. It quickly submerged and re-appeared near the HMAS Canberra off Farm Cove. At 11 pm, air raid sirens sounded all over the city. Searchlights moved over the harbour and gunners began to fire. Sydney residents hid in their air-raid shelters. The last Manly ferry had departed from Circular Quay with 27 passengers as the shooting began. Luckily, no one was injured.
 
At 11.14 pm, a blackout of the ships was ordered so that any attacking submarine would not be able to see them. The guns stopped firing at 11.15 pm.
 
The Midget submarine dived to the bottom of the harbour to wait for the alarm to die down.
At 12.15 am, Ban's Midget submarine re-emerged between Bradley's Head and the USS Chicago. At 12.30 he fired his two torpedoes at the American ship, which was 500 metres away. Both torpedoes were useless - the first shot passed the Chicago and embedded itself in the shore of Garden Island, failing to explode.
 
The second torpedo passed five metres ahead of the ship, underneath a Dutch submarine, and exploded on Garden Island.
 
Although the torpedoes did not sink the Chicago, the explosion on Garden Island was strong enough to sink the ferry HMAS Kuttabul which was docked at Garden Island, killing 19 Australians, two British sailors, and wounding tenothers.
 
The Japanese Midget submarine then disappeared. It is thought that it left the harbour at around 1.58 am to return to the mother submarine.
 
The third Japanese Midget submarine, the M22, was commanded by Matsuo Keiu. At 11 pm, the submarine attempted to enter Sydney Harbour but was attacked by HMAS Yandra. The submarine sustained some damage and retreated for four hours. Keiu tried to re-enter the harbour at 3 am and was seen by the USS Chicago. The second entry of the M 22 led some people to believe that four Japanese submarines were entering Sydney Harbour.The Kanimbla, a British merchant ship, shot at the Japanese submarine at Neutral Bay.
 
The submarine again disappeared until it was spotted at 5 am by the patrol boat Sea Mist at Taylor's Bay, the rendezvous point for the Japanese submarines. The Sea Mist pursued the submarine and, as the Midget dived to the bottom of the harbour, Sea Mist dropped two depth charges. The explosions damaged the submarine, but also the Sea Mist. The ship Steady House took over and further disabled the submarine.
 
It was a frightening end for Matsuo Keiu and his co-pilot Tsuzuku. He attempted to explode the submarine, but there was too much water flooding through the damaged hull. He could not escape because the conning tower hatch was stuck. The two men committed jiketsu, an honourable form of suicide, by shooting each other. The submarine was retrieved from the water by Australian ships three days later. See animation

Other submarine attacks

The night of 31 May 1941 did not bring the end of Japanese naval incursions in Australian waters.

There were several revenge attacks on the eastern suburbs of Sydney and Newcastle. In the following days, eight Australian ships were attacked by Japanese vessels along the east coast of Australia, from Bairnsdale in Victoria to Cape Moreton in Queensland.
 
Three ships were sunk and 49 people died. On 7 June 1941, a Japanese destroyer fired seven shells on the eastern suburbs. Although five failed to explode, a man in Bondi broke his leg, and a block of flats in Vaucluse were damaged.

The attacks frightened Sydney residents, causing some to move west to the Blue Mountains, even as far as Orange. By the end of the War in December 1944, as many as 27 Australian ships had been sunk by Japanese-sown mines and torpedoes. 577 had been killed.

After the attacks

When the Japanese Midget submarine was raised and the two dead Japanese officers were discovered, the Australian authorities decided to give the officers a military funeral.

On 9 June 1942 at the Eastern Suburbs Crematorium, four coffins - two for the retrieved bodies, and two for the submarine that disappeared and probably sank - were given a formal military burial. The ashes were given to the Japanese ambassador.
 
The Australians treated the Japanese submariners with the respect due to officers of a military force, recognising their bravery, and hoping that, in return, the Japanese officers would treat Australian prisoners of war with respect. See image 3

A funeral for the lost submariners took place in Japan in October 1942. The six submariners who died were posthumously promoted two ranks, made into demi-gods and worshipped as heroes.

The M24 submarine was not seen again and was thought to have left Sydney Harbour to dock with its mother submarine. In November 2006, however, a group of amateur divers discovered the M24 submarine in Sydney Harbour. The submarine was intact and is presumed to contain the bodies of the two Japanese crew. The future of the submarine is being discussed between the Australian and Japanese governments.  Regardless of whether the M24 is raised or not, its discovery brings closure to an episode in Australia and Japan's war history.

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Question 1/5

1. How many midget submarines entered Sydney harbour on that evening?

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