The Japanese Invasion Threat of Australia


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Japanese intentions to invade mainland Australia during World War Two have long been the subject of passionate debate amongst historians worldwide. Some scholars are convinced that the Japanese had made solid preparations to invade mainland Australia but their plans were thwarted by the Allied victory at the Battle of the Coral Sea. Others state that the Japanese were too busy consolidating their position in South East Asia in preparation for the inevitable entry of significant US forces in the region. The theories touted by both of these parties are irrelevant for our purposes. Regardless of their actual intentions, the Japanese “Jungle Blitzkrieg” so seriously concerned Allied military planners that significant resources and manpower were concentrated on the defence of Australia. The important issue is that Australia was fortified for invasion and that plans were drawn for a guerrilla campaign to wear out the Japanese forces before an allied counter attack.

It is a matter of historical record that Australian government and military planners were deeply worried about the prospect of a Japanese invasion and extensive plans and “defence schemes” were devised to defend Australia in the event of large areas of the mainland being occupied by the Japanese. It is known that part of these plans involved pre-positioning stockpiles of civil relief materials and food for use by civilians and military personnel caught in areas of the Australian Mainland overrun by the enemy.

Australian Intelligence had received reports from Chinese and US sources, which seemed to confirm our government’s worst fears. The Curtin government openly admitted its concerns to its citizens and implemented a massive civil defence program. This was accompanied by public announcements about the Japanese threat as evidenced by official posters, pamphlets and radio recordings that exist at the Australian War Memorial in Canberra.


It’s Fight, Work or Perish!
The enemy Thunders at our very gates. Everything we cherish is in immediate peril.

As Australia’s leader I can no longer wait to argue with you, appeal to you or reason with you. There is no time: the danger is too great.

Strikes, lockouts, provocation, profiteering and exploitation increase our national danger. They must cease. What we have done, or are doing, is not as good as what we can do–should do–and must do.

You must make complete sacrifice for Australia or become a complete sacrifice to the enemy.

It’s fight, work–or perish.

Rt. Hon. John Curtin, Prime Minister of Australia.

Australian Government’s position on the threat of a Japanese invasion of Australia may not have been far off the mark as originally thought.

New information has come to light suggesting that the the Australian Government’s position on the threat of a Japanese invasion of Australia may not have been far off the mark as originally thought.

According to a United States Office of Strategic Services (OSS) report from October 1942, the Japanese were actively planning an invasion of Australia in June or July 1942. The OSS report is based upon information secretly passed to an OSS asset by neutral Spanish diplomatic staff in Tokyo.

The report extract below appears to be derived from minutes of a Japanese Imperial War Council meeting and details Japanese motivations for carrying out such a costly operation.

The costly lesson learned by the Japanese during their attack at Midway has resulted in the opinion, apparently held by Admiral Suetsugu, that surface operations even with carrier air support cannot successfully be carried out within 750 miles of a strong enemy base of shore-based aircraft. He believes that the Japanese possessions in the Western Pacific can only be made impregnable by concentrating on the strengthening of their air defence and that only Australia remains as an obstacle to the creation of a perfect defensive chain. However, he appears to have felt that Australia has already been reinforced to such an extent that operations designed only to isolate it would cause such heavy losses that its subsequent invasion would be rendered impossible.

The above opinion, claimed to have been voiced at a meeting of Japan’s policy-makers, was in general agreed to by other members, but it was felt that regardless of losses, Australian invasion plans must be pursued. General Tojo, the Prime Minister, agreed that Australia must be reduced.  General Asaka and General Terauchi supported General Tojo, but pointed out that unless Fiji, the New Hebrides and New Caledonia were soon captured, such a plan would have little chance of success and the Japanese gains in the South West Pacific Area would become increasingly endangered. General Tojo expressed the opinion that in order to cut down the losses of naval operations against the Australian mandates, a simultaneous attack by the landing of a massive expeditionary force at several points on the Australian mainland should be undertaken.

In December 1942, Chinese Intelligence sources provided details of what appears to be the general strategic concepts of the proposed operation. The Japanese Military Headquarters had drawn up plans for a large-scale military incursion into the Australian mainland in mid 1942. The concept of the operation was described as follows:

The base of operation was to be situated in the areas comprising the Nan Yang (South Seas) and New Guinea. By adopting a defensive strategy against the US naval forces the Japanese hoped to be able to defend their left flank. The main defence for this flank was a massive minefield in the Straits of Malacca. This would effectively block any naval force attacking the Japanese supply areas from the Indian Ocean.

A force consisting of warships and transports was to make a lightning attack on Darwin in the hope of drawing US and Australian forces into the isolated areas between Katherine and Birdum. Then the main invasion force would set out from Sunda Strait and Christmas Island and land on the Australian coast in the vicinity of Fremantle. The Japanese would then attempt to control the railways and harbour facilities west of Esperance Bay and Sandstone before advancing eastward.

The operation was originally planned to take place in mid-June 1942 with Japanese military supplies stockpiled at a large base at Java in the Netherlands East Indies (now the Republic of Indonesia). Japanese troop transportation and reception centres were established throughout the area and plans were drawn to secure the sea and air routes down the Northwest coast of Australia.

The attack was apparently postponed on account of US-led counter-attacks such as the Battle of the Coral Sea and once the Japanese started to lose their initiative and were forced to concentrate on defending the areas they had already annexed, the Invasion of Australia plans were never implemented. The authenticity of the invasion plan as described by the Chinese sources is a matter of contention.

Some academics argue that the plan above is a fake and that the Chinese may have thought that an authentic-looking Japanese invasion plan might have forced the Allies to fast-track plans to clear the enemy from Southeast Asia. This would have helped make China a major theatre for Allied operations rather than the Southwest Pacific. The truth is almost certainly lost to the mists of time, but the plan is included here to illustrate the kind of intelligence acted upon by the Curtin government. It certainly helps to explain why the Australian government was publicly discussing a pending Japanese invasion well into 1944 when, as we know now, the Japanese were barely capable of defending the Japanese Home Islands, the Philippines and their Mandated Territories.

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