287 Mr John Curtin, Prime Minister, to Mr Winston Churchill, U.K. Prime Minister
Cablegram Johcu 19 CANBERRA, 21 January 1942
MOST IMMEDIATE MOST SECRET
Reference Winch 6, paragraph 4. 
I have obtained the views of our Chiefs of Staff on the danger of invasion and the reinforcement of our home defence forces. They are as follows:-
THE DANGER OF INVASION OF AUSTRALIA IN FORCE 1. So long as we retain a foothold in Malaya and the Islands of the Malay Barrier remain in our hands we do not consider that Japan will attempt a major attack against Australia. Her method is likely to be the step by step policy which has so far had conspicuous success. But, with the land, sea and air forces at her disposal and the merchant shipping she has available, the direct move towards Australia from bases in the mandated islands grows more probable. This is also likely to take the form of a progressive southward move securing New Guinea, New Hebrides and New Caledonia as advanced bases from which to sever our sea communications and from which a major attack could be launched on Australia if and when the strategic situation in the area of Malaya and Netherlands East Indies is judged to be suitable.
2. In this connection, the United States [of] America [Pacific] fleet has to be considered. Although it has obviously suffered severe material and moral damage, we do not consider that, until a decisive fleet action has resulted in favour of Japan, the latter would attempt a sea movement, from advanced bases in the Islands to the north and north-east, of the size necessary for a major attack on the mainland of Australia.
3. Our immunity from invasion accordingly depends on our ability to maintain our position in Malaya and the Netherlands East Indies and on the threat of the United States [of] America [Pacific] fleet against the long Japanese sea lines of communication to the South. These are imponderable factors, but, in view of what has happened since the outbreak of war with Japan, it would be folly for us to suggest that these factors will operate in our favour.
It is a race against time in Malaya in which the enemy will do everything possible by air and submarine attacks to prevent our reinforcements getting through. Should we lose Singapore, our prospects of retaining Sumatra would be poor. Lastly, control of the Pacific can be won or lost in one fleet action.
4. We therefore consider that the danger of invasion in force will remain until we have clearly stabilised our front along the Malay barrier or until we have secured supremacy over the Japanese fleet.
THE REINFORCEMENT OF THE HOME DEFENCE FORCE 5. The great extent of our vulnerable coastline renders inevitable a very large degree of dispersion of our land and air forces. The reserves available are therefore limited in number and are further limited in scope owing to the distances over which they may have to be moved to meet any serious threat.
6. Should Japan secure complete freedom of the seas, the only limit to the forces she could employ against us would be that imposed by the amount of shipping available to her.
7. It is clearly beyond our capacity to meet an attack of the weight that the Japanese could launch. At the same time, our limitations in both manpower and equipment deny us the capacity to increase our land forces to an appreciable extent. Any reinforcement, provided it is adequately trained and equipped, must increase our security by providing a greater deterrent to attack.
8. We assume that if the proposal is implemented American troops would be subject to the Chief of the General Staff in respect of training and operations.
9. Apart from the question of Australian security, Australia is an admirable base for reinforcements for offensive action against the Japanese in the South-West Pacific area, and it is desirable that forces available for this purpose should be located here as soon as possible.
The War Cabinet and the Advisory War Council welcome the suggestion that our land forces should be reinforced by American formations.  We assume that their full equipment would be provided by the United States [of] America Government. We should like to make it clear that the provision of United States troops alone in the strength which you indicate is not of course the sole measurement of our needs. We have, as you are aware, serious deficiencies in aircraft and other equipment about which we have already made representations through our representatives in London and the United States [of] America.