71 Lord Cranborne, U.K. Secretary of State for Dominion Affairs, to Commonwealth Government
Circular cablegram M308 LONDON, 19 September 1941, 10 p.m.
IMPORTANT MOST SECRET
My Circular M.285 of 2nd September. 
We have now given full consideration to the question whether it would be desirable to convey a formal warning to Japan as to the consequences which would follow any further encroachments on their part in the Far East.
It will be remembered that in his broadcast of 24th August the Prime Minister  referring to the menace created by Japan's latest expansionist activities said 'it is certain that this has got to stop' and added that if the efforts of the United States to bring about an amicable settlement in the Far East failed 'we shall of course range ourselves unhesitatingly at the side of the United States'. This followed communication by the United States Government of a memorandum to the Japanese Ambassador at Washington  which closed with a warning in terms given in my telegram [M].  268 of 27th August. 
A subsequent discussion with the United States Secretary of State  indicated that the United States Authorities would prefer that we should not link up any warning on our part with theirs but that they would prefer us on the other hand to adopt a formula which would be as wide as theirs and would omit mention of the word 'war'.
We have ourselves reached the conclusion in the present circumstances no useful purpose would now be served by issue of a warning by us at once so wide and so relatively vague as that of the United States. We feel that this would add nothing to the warning conveyed already in the Prime Minister's broadcast and may even detract from its force. The broadcast made clear both our attitude towards the Japanese expansionist policy and our complete support of the United States and has, we feel sure, been taken by the Japanese Government as complementary to the United States warning. Unless therefore events show the need for something more, we consider it better to let the matter rest where it is.
We should propose therefore that the United States Government be informed accordingly. It is however important that the United States Government should be given no grounds for thinking that we had not taken action in this matter fully corresponding to their own. We propose therefore to word our communication so as to indicate that if they thought that we could usefully make any further statement we would do so but that in our judgment it was undesirable to add anything at this stage to the Prime Minister's broadcast.
We should be glad to learn as soon as possible whether His Majesty's Governments in the Dominions concur in a communication being addressed to the United States Government on the above lines.