Japan. British Ambassador in Tokyo  sent on March 23rd his views on the best policy to follow in the Far East in view of the renewed threat of European war.
Assuming that Japan has not yet undertaken any further commitments in negotiations at Berlin he thinks that if war broke out in Europe she might well prefer to watch the progress of preliminary operations before deciding finally what course to adopt, but she would probably not remain neutral for long in any war in which U.S.S.R. were engaged.
The United Kingdom should therefore try to keep her neutralised and for the present Japanese opinion should not be irritated unduly by formal protests except on matters of first importance.
At the same time United Kingdom should show strength wherever possible by action such as the following :-
(a) Naval and Air. He presumes that on outbreak of war every effort will be made to send a capital ship squadron to the Far East not only to co- operate in defence of Singapore but to support cruiser action for defence of southern trade routes and communications with Australia and New Zealand. He urges that instead of awaiting outbreak of war capital ship squadron should be sent at earliest possible moment. He feels in addition to other advantages such action at this juncture would afford powerful deterrent against Japanese co- operation with axis powers. It would destroy the false impression in Japan of British naval impotence in Far Eastern waters even on the assumption that no more than three capital ships could be spared for the purpose. Furthermore the presence of adequate fleet and air force based on Singapore would, by removing chances of rapid attack on Singapore, also remove one of the prizes [of] war and so enhance in Japanese eyes the advantages of neutrality. He feels that the step would have to be unostentatious and be explained to Japanese Government beforehand (prior notification was beneficial in case of Chinese currency fund).
(b) Political. If it were possible to arrange early start of conversations for defence of Malaya, Indo-China and Netherlands East Indies between British and Australian authorities on the one hand and French and Netherlands on the other, the fact that such action was being taken would have a determined [sic] effect on any Japanese plans to acquire territory in South while powers were busy in Europe.
(c) Economic measures should be taken jointly with United States and France in hope that a foretaste of economic blockade would make Japan unwilling to risk economic dislocation consequent on opposing the democracies.