The most important part of the document, COS(40)592, was addressed to the British commander in chief in the Far East, Air Marshal Robert Brooke-Popham. It indicated that Britain would not go to war against Japan, even if the Japanese were to invade French Indochina. The document also stated that the British Chiefs of Staff regarded both Thailand and Hong Kong as indefensible against Japanese attack.
Bernhard Rogge, the captain of the Atlantis, recognized the significance of these papers and sent them on by ship to Kobe. They were then delivered to German naval attaché in Tokyo Rear Admiral Paul Wenneker, who forwarded them to Berlin. There Adolf Hitler ordered the information passed to the Japanese, and Japanese naval attaché Captain Yokoi Tadao sent a summary of the documents to the Navy Ministry in Tokyo.
On 12 December 1940, Wenneker handed the documents to Vice Admiral Kondo Nobutake, the Japanese navy vice chief of staff. Wenneker also stressed the weak British military posture in Asia and conveyed to Kondo Hitler's suggestion that the Japanese attack Singapore.
There is no doubt that these documents encouraged the Japanese leadership in its decision to advance into Southeast Asia in 1941. They convinced the Japanese naval minister, Admiral Oikawa Koshiro, that Britain would not wage war with Japan over French Indochina. Kotani Ken
CAB 66/10, Public Record Office, Kew, UK.; Chapman, J. W. M. "Japanese Intelligence 1918–1945." In C. Andrew and J. Noakes, eds., Intelligence and International Relations 1900–1945. Exeter, UK: Exeter University Press, 1987.; Elphick, Peter. Far Eastern File. London: Hodder and Stoughton, 1997.; Rusbridger, James. "The Sinking of the Automedon and the Capture of the Nankin." Encounter 375, no. 5 (May 1985): 8–14.