British Cryptanalysis and China, 1937–1945: An Underused Source for Recent Chinese History?

Abstract

This article discusses British cryptanalysis of Chinese diplomatic traffic, and of the diplomatic traffic of other states such as Japan and Afghanistan regarding China, between 1937 and 1945. The records are in the British National Archives HW12 series, which has not been thoroughly exploited by historians due to inadequate cataloging. The article shows how British and American views on the failings of Chinese communications security, which led to much-resented restrictions on Chinese diplomatic reportage and a general reluctance to share high-level information with China, were informed partly by the extent of Japanese mastery of Chinese traffic, which was in turn disclosed through British and American successes against Japanese communications. Finally, Chinese and Japanese efforts to court Muslim opinion internationally are discussed to illustrate how material in HW12 can make a useful contribution to the study of diplomacy and intrigue during the Second Sino-Japanese War.