Top Secret
5 December 1941
From: CNO
Action: Spenavo London

While CNO agrees with you that November reports of a Japanese concentration in the Pelews were unfounded, the possibility of an attack by the Japanese from that region against the Philippines or Nei cannot be ruled out. This replies to your 031411 and gives CNO views as to the military aspects of the Dutch project to declare areas south and west Davao dash Waigeo dash equator line dangerous to shipping in order that Dutch forces might attack suspicious vessels entering from north and east. Were this area declared dangerous to shipping the prohibition would apply to all merchant shipping of whatever nationality and to naval vessels of the United States and United Kingdom as well as to those of Japan. Large amounts of shipping traverse this general area and it is questionable if Dutch could set up promptly a naval control system that would obviate excessive delays of shipping most important to the United States and particularly shipping carrying United States naval and army reenforcements to the Philippines as all United States shipping between west coast of United States and the far east area is now routed via Torres Strait. If NEI declares this large area closed it would be quite a different matter from the British closure of the Jahore area which is a very small one. Japan would be free to close Okhotsk Sea, the Sea of Japan, and all the western portion of the South China Sea and the Gulf of Siam. Were the United States to acquiesce in the Dutch declaration it would have few grounds for objecting to a Japanese declaration of the same character. At present United States defense aid is going to Russia via the Okhotsk Sea and the Sea of Japan, and the United States, United Kingdom, and Netherlands East Indies are executing extensive reconnaissance measures in all directions considered dangerous. Shipments to Siberia and reconnaissance measures ought to continue and CNO is convinced a declaration by the Dutch closing the area in question would be most prejudicial to naval and military interests of the three powers. If Dutch authorities consider some warning should be given Japan CNO believes it should take the form of a declaration to Japan that in view of the current situation Japanese naval vessels or expeditionary forces crossing the Davao Waigeo line would be attacked. Communicate these views to the admiralty and the Dutch naval command in London.