316 Mr R. G. Casey, Minister to the United States, to Department of External Affairs
Cablegram 151 WASHINGTON, 21 February 1941, 10.10 p.m.
FOR CHIEF OF NAVAL STAFF. 
FROM NAVAL ATTACHE 
Fourth Progress Report.
Following is summary of the United Kingdom Delegation appreciation, vide paragraph (2) of my telegram 117 , begins.
Maintenance of fleet base at Singapore cardinal point in British strategy. Stratagem based not only on pure strategy but political, economical and colonial considerations which even if not vital on strictly academic view are of such fundamental importance to the Empire that they must be taken into serious account.
Compare with the United States attitude to the defence of the Western Pacific area. The Empire is comprised of various Dominions and Colonies held together by communications and trade routes across the oceans.
Home population depends on imported food and overseas trade.
Security and prosperity of India our trust and responsibility.
Defence of all these interests, vital to the maintenance of the associated war effort, depends on the capacity to hold Singapore, and in the last resort to base the battle fleet there.
2. Until recently it was the policy of the United Kingdom Government to despatch the fleet to the Far East on the outbreak of war. This now impracticable. If the United States do not come in we would hope to hold out in Malaya for a long time though the air forces there are far below the strength required. But if Singapore in serious danger of capture and the United States still withheld aid, we should be prepared to send the fleet to the Far East even if this would compromise or sacrifice the position in the Mediterranean.
3. Active intervention of the United States would profoundly modify the situation. If the United States Navy were active in the Pacific, invasion of Australia and New Zealand would be precluded.
These Dominions would only withhold their collaboration in the war effort in the last resort and, with the United States active allies, proportion of their trade and military contribution could be transported eastward across the Pacific provided the United States Navy could ensure reasonably safe passage.
4. In reply to the argument which was put forward by United States representatives in the discussion we agreed that the Japanese with a hostile United States fleet on their flank would not base the main fleet on captured Singapore; that even if we retained Singapore, the Japanese operating from Kamranh Bay or Batavia would threaten seriously our Indian Ocean communications and that we could afford measure of protection to those in the Western Indian Ocean from Colombo but not as much as if we can use Singapore.
5. If the United States intervene we might thus still hope to maintain cohesion and the war effort of the British Commonwealth of Nations without abandoning the position in the Mediterranean.
We still consider the issues at stake so fundamental that the loss of Singapore would be a disaster of the first magnitude, second only to the loss of the British Isles.
6. Then stressed the importance of Singapore [card of re-entry, so that if]  threat in the Indian Ocean and Western Pacific [became] intolerable [w]e could still accept risks elsewhere and send the fleet. Failure to do so would mean that Japan becomes the undisputed master of East Asia, Netherlands East Indies and Western Pacific. Empire and United States would lose resources in food and vital irreparable war materials. Japan would become self- supporting and the United States economic weapon useless. Our morale and prestige would suffer resounding blow with grave consequences during and after the war. All hope of Chinese resistance would end and Russia might throw in her lot with the Axis. India and Burma would become a liability. Unless we retain this foothold, even if Italy was eliminated and Germany defeated, highly problematical whether we could ever undertake combined operations necessary to restore the position in the Far East after an exhaustive and desperate struggle.
7. We then went on to give Japanese courses of action, suggesting Japanese plan was to avoid implicating United States and possibly Dutch and to attack Malaya. In reply to the question as to how long Malaya could hold out we discovered imponderable factors, namely, stage at which United States might intervene, whether or not the Dutch would fight; effect of the present deficiencies in our forces in the Far East and the ability of the joint Asiatic forces to neutralise the Japanese forces in the South China Seas, and the extent to which operations of the United States Pacific fleet would contain Japanese forces in the North. We stressed the need for the fleet to undertake active operations against Japan and finally pressed home the point that the Asiatic fleet required reinforcements if it was to constitute a real menace to the Japanese advanced sea communications.
8. In reply to further United States arguments put forward in the discussion we went on to discuss the meaning of their phrase 'holding the Malay barrier' and minimum forces required. No question of sustaining the whole of our position in the Far East.
For instance no hope of retaining Hong Kong, Philippines or Borneo indefinitely. Irreducible minimum which must be held was Singapore, and to do this must deny the Japanese uninterrupted freedom of action to carry out sustained operations in the waters and from territories surrounding Singapore.
Japanese attack on Malaya would involve sustained operations with large land and air forces and establishment of naval control in South China seas. Such operations would not be carried out satisfactorily without capital ships in South China Seas if effective associated naval forces were operating from Singapore and any possibility remained of capital ships appearing in those seas.
9. Strength of Asiatic forces must be determined to some extent by strength of forces that may not be contained by operations of United States Pacific fleet. The only real solution is capital ship force at Singapore. Realizing, however, that there were initially many real difficulties we pointed out that, in view of the weakness of the British and Dutch forces, essential that we should be able to gain time to move land and air reinforcements to Malaya when the emergency arises or in last [resort] adjust and concentrate necessary naval forces.
10. We should therefore be in a position to dispute the Japanese control of the sea communications in the South China Seas. In the absence of capital ship force this can only be done if United States or British Asiatic Naval Forces are reinforced to an extent which would constitute a real threat to the Japanese advanced sea communications and enable us at least to interrupt them.
Naval reinforcements of the order of one carrier, a division of heavy cruisers and auxiliary craft in proportion would be minimum required to fulfil this role in early stages.
11. In view of the fact that the main theatres will be the Atlantic and Mediterranean obviously desirable that naval reinforcement of Asiatic forces should not be at the expense of these areas which means that it should be found from United States Pacific Fleet. Fleet must be strong enough to fulfil its strategic function, i.e. contain rival forces away from South China seas;
but distances involved are immense and if Japanese are to conduct serious operations in South China seas they will be compelled to make substantial detachments from their main fleet including capital ships. It is suggested therefore that the small reduction in the strength of Pacific fleet proposed above could be accepted without weakening the capacity of main fleet to fulfil its offensive role, exposing United States interests to attack or exposing United States naval forces to insecurity. (This in reply to points made in discussion).
12. Then expressed our conviction that if United States Pacific Fleet was to draw off Japanese from sustained operations against Malaya it was essential that it should be extremely active in Japanese waters and against Japanese mainland.
13. Finally, we invited the United States representatives to agree with the contention of His Majesty's Government in the United Kingdom that security of the Far Eastern position, including Australia and New Zealand, is essential to the maintenance of the war effort of associated Powers. Singapore is the key defence of these interests and its retention must be assured.
Summary of United States staff committee's written reply will be telegraphed shortly.