Moresby. On 23 April Fabian showed MacArthur that the IJN was amassing a large force at Truk, and planned to occupy Tulagi also. MacArthur got an Australian reconnaissance plane to "discover" the Port Moresby invasion force on 5 May, leading to the Battle of the Coral Sea. On 19 and 23 May messages indicated that the Japanese were proposing to land at Buna and go overland over the Owen Stanley Range via the Kokoda Track to Port Moresby; though MacArthur, Willoughby and Blamey were unconvinced saying "Nobody in their right senses would land there". Blamey took "minimal precautions" to defend the track, resulting in heavy losses for the 39th Battalion sent there. Central Bureau's origins Central Bureau was a joint US-Australian signal intelligence organisation, established on 15 April 1942 under the command of US Army Major General Spencer B. Akin, with headquarters in Melbourne. General MacArthur advised Washington of his decision in a dispatch on 1 April 1942. He described the role of the group as "the interception and cryptanalyzing of Japanese intelligence". A small Naval cryptographic group also became part of the secret new unit. It was led by Commander Eric Nave, who with Professor Dale Trendall had been working on Japanese diplomatic and naval codes at Victoria Barracks. Central Bureau was established in a gabled, ivy-clad mansion called "Cranleigh" in Domain Road, at South Yarra, Melbourne. Central Bureau's role was to research and decrypt army and air intercept traffic and work in close co-operation with other SIGINT centres in the USA, United Kingdom and India. Mic Sandford was appointed AIF Commanding Officer at Central Bureau. Major General Akin's Executive Officer, Major (later Colonel) Joe R. Sherr had been evacuated from the Philippines (Station 6). He was responsible for arranging for the first group of US "SIGINT" personnel to come to Australia, and as Akin's control was indirect he was responsible for day-to-day running of the bureau. He was killed when returning from a liaison visit to the wireless Experimental Centre in India, when his aircraft crashed 3 km from Calcutta airfield on 21 September 1943. Sandford had wanted to send "Pappy" Clark to the conference but Akin said that MacArthur would not agree to send Clark (only a major) and so sent Colonel Sherr instead. He was succeeded by Major Abraham "Abe" Sinkov, a mathematician, who was appointed assistant director of Central Bureau. Sinkov had previously been a