 The Japanese were aware of the state of the Singapore defences . There were spies in Singapore , such as Captain Patrick Heenan , and a copy of the Chiefs of Staff 's August 1940 appreciation was among the secret documents captured by the German surface raider Atlantis from the SS Automedon on 11 November 1940 . The report was handed over to the Japanese , and the detailed knowledge of Singapore 's defences thus obtained may have encouraged the Japanese to attack . 
