Background
During the Second World War major radio masts appeared at Rockbank (Army Receiving Station) and Diggers Rest (Army Transmitting Station), about 40 km west of Melbourne. The Americans established these stations, or bases, which were intimately associated with events of great historical importance to Australia.  

The surprise Japanese air-raid on Pearl Harbour on December 7 1941 had created a new Pacific arena in the Second World War, and brought the United States into the conflict.  In the following months the Japanese conducted lightening advances throughout South East Asia  including, on  February 15 1942, the defeat of the British fortress at Singapore.  Four days later the Japanese carried out the first of their bombing raids on Darwin. 

This crisis impelled Prime Minister Curtin to make his historic declaration that Australia’s future would now depend more on its relationship with the USA than with Britain.  In March 1942 US General Douglas MacArthur arrived in Australia to co-ordinate the war against the Japanese.  Australia’s war effort was being controlled from Melbourne’s Victoria Barracks on St Kilda Road, and MacArthur also established his headquarters in Melbourne.

These were Australia’s dark days, of slit trenches in parks, concrete air raid shelters and city ‘brown-outs’.  

In May 1942 Japanese midget submarines attacked Sydney Harbour. 

International radio communications were vital to the establishment of US headquarters in Melbourne.  By April 1942 survey works for radio stations at Diggers Rest (transmitting) and  Rockbank (receiving) stations had been completed.  

In April four rhombic aerials, mounted on sixteen 30 metre masts, were commissioned at both Diggers Rest and Rockbank to connect US command with ‘Panama, Pearce, Washington, and Bombay (India)’.

After conquests throughout Asia - in China, the Philippines and Singapore - the focus of the Japanese by late 1942 was the invasion of New Guinea, where they were met by Australian and US forces. Two key naval battles dealt a major blow to the Japanese offensive. The Battle of the Coral Sea in May, while inflicting equal damage on both sides, repelled the Japanese naval assault on Port Moresby. In the Battle of Midway in June, the US and allied forces inflicted a major defeat on Japan.   

While the New Guinea campaign continued throughout 1942, these naval battles represented a turning point in the war. MacArthur pronounced that the allied forces recapture of Sanananda in northern New Guinea in January 1943 signalled the start of the Japanese collapse. 

US forces were now on a northward offensive, on an island hopping campaign in the central and south Pacific. Their infrastructure, including radio communication facilities, moved north with them. The Diggers Rest and Rockbank stations were no longer of use to the US military command. On January 12 1943 an Australian War Cabinet agendum advised that the Australian Army had recently taken possession of the Diggers Rest and Rockbank radio  stations, and their cable connections to the city communications centres.

The rhombic aerials inherited by the Australians from the Americans had been directed at Darwin (and ‘Chunking’), Townsville and Port Moresby, London, San Francisco and Noumea.

By the war’s end the stations were the Australian Army’s link with London and other Commonwealth centres in South-East Asia (Delhi, Kandy, Singapore and Welllington), and Rabaul in New Guinea.  In the immediate post-war period, Diggers Rest and Rockbank were also the lynch-pins of communication between the British Commonwealth Occupation Forces, handling all UK, NZ and Indian traffic between Melbourne and Japan (Kure). 

In the late 1940s into the 1960s the Diggers Rest and Rockbank stations were ‘the radio transmitting and receiving centres of the Australian Relay Station of the Empire Army Wireless  Chain and the AMF communication system.’