'1942, Australia’s greatest peril'

He said that after he had taken Singapore, he wanted to discuss with Tojo a plan for the invasion of Australia … Tojo turned down the plan, making the excuse of lengthened supply lines, which would be precarious and open to enemy attack …

Yamashita’s plan to conquer Australia was practically identical with his successful campaign in Malaya. He intended to land on each side of the major Australian cities and cut them off, first making a series of dummy landings to draw off the pitifully few Australian troops.

“With even Sydney and Brisbane in my hands, it would have been comparatively simply to subdue Australia. I would never visualise occupying it entirely. It was too large. With its coastline, anyone can always land there exactly as he wants” ... Yamashita said.

The influential hard-liner, Admiral Takasumi Oka, head of the bureau of naval affairs within Naval General Staff in Tokyo, vehemently disagreed with Army plans to maintain a defensive stance:

[We] need to actively move our forces to Australia and Hawaii, annihilate our enemies’ marine military force, and decimate our enemies’ bases for counterattack … it is vital that we procure resources within the co-prosperity sphere and ensure that they are not taken by our enemies …

Bitter debate continued about Australia between the Army and the Navy. The Army’s chief of staff General Hajime Sugiyama, who took minutes of vital planning meetings in March 1942, summarised:

Put simply, the Navy argued for an aggressive offensive that included attacking Australia, whereas the Army outright opposed attacking Australia, stating that the focus ought to be on firmly establishing the situation so that Japan will be unbeatable in the long-term.

General Sugiyama when referring to “attacking Australia” was in fact speaking about invasion because at the time of writing, Darwin was already being bombed from the air.

After the war, awaiting trial for war crimes, ex-Prime Minister Hideki Tojo said Japan never had plans to invade Australia. But Prince Naruhiko Higashikuni, an uncle to the Empress Nagako, tells a much different story in his memoirs. Higashikuni, a member of the Supreme War Council, wanted Japan to quit while ahead. He told Tojo after the initial successes that Singapore would soon fall and Japan should start peace overtures, adding: “We must end this war without further delay.” According to Higashikuni, Tojo was defiant, replying:

I think we will have few problems occupying not only Java and Sumatra but also Australia if things go on like this. We shouldn’t think about peace at this time.

The critical debate about the invasion of Australia took place between late January and mid March 1942. During this period the Imperial army and navy were in constant disagreement. In time the Japanese Imperial Army gained the upper hand in the invasion debate about Australia, although the Navy refused to abandon the idea, considering it for some time merely to be shelved.

But as a compromise in the debate, the Imperial Army agreed to more easily achievable and realistic goals, including the invasion of the Australian base of Port Moresby. Prime Minister Tojo, General Sugiyama and Admiral Nagano put a compromise solution to Emperor Hirohito on March 13.

The Army allowed inclusion in the text of a “temporary invasion of Darwin” as a future option to demonstrate “positive warfare”. But the “temporary invasion of Darwin” proposal had so many tough Army conditions attached, including the need for major victories elsewhere, that of itself it would not lead to invasion of Australia’s north.

As I state in 1942, Australia’s greatest peril, Japan’s devastating losses in the Battle of Midway significantly helped to secure Australia’s safety, along with battles at Kokoda and Milne Bay, among others, but the threat had been very real. As David Horner, professor of Australian defence history, speaking at a Canberra seminar in 2002 about the period January to March 1942, said:

The events of 1942 presented the Australian government and its military high command with greater challenges than at any time since Federation. For the first and only time since white settlement Australia faced the prospect of a foreign invasion.