Fleet Radio Unit, Melbourne (FRUMEL) was a United States-Australian-British signals intelligence unit, founded in Melbourne, Australia during World War II. It was one of two major Allied signals intelligence units, called Fleet Radio Units, in the Pacific theatres, the other being FRUPAC (also known as Station HYPO), in Hawaii. FRUMEL was an US Navy organisation, reporting directly to CiCPAC (Admiral Nimitz) in Hawaii and the Chief of Naval Operations (Admiral King) in Washington,  and hence to the central crypographic organization. The separate Central Bureau in Melbourne (later Brisbane) was attached to (and reported to) MacArthur's Allied South West Pacific Area command headquarters.
FRUMEL was established at the Monterey Apartments in Queens Road, in early 1942, and was made up of three main groups. First was Lieutenant Rudolph J. (Rudi) Fabian's 75-man codebreaker unit, previously based at the United States Navy's Station CAST in the Philippines before being evacuated by submarine on 8 April 1942. The second was Commander Eric Nave's small Royal Australian Navy-supported cryptography unit, which had moved to the Monterey Apartments from Victoria Barracks in February 1942. Nave's unit was made up of a core of naval personnel, heavily assisted by university academics and graduates specialising in linguistics and mathematics (including from June 1941 a "cipher group" of four from Sydney University). These included Thomas Room, Dale Trendall, Athanasius Treweek, Eric Barnes, Jack Davies and Ronald Bond. The third group was a trio of British Foreign Office linguists (Henry Archer, Arthur Cooper and Hubert Graves), and Royal Navy support staff, evacuated from Singapore, particularly from the Far East Combined Bureau (FECB) there. IBM (punched-card) tabulating machines were obtained in 1942 to replace that left behind in Manila Bay on leaving Corregidor.
Nave and Fabian had a difficult relationship, and Nave eventually joined the Army’s Central Bureau at Brisbane. According to Jenkins: Fabian wasted no time in getting rid of the civilian supernumaries at Monterey, many of them British service wives who had been evacuated from Singapore. He also squeezed out the British diplomatic corps types like Cooper and Archer. Eventually he seems to have succeeded in ousting Nave, who went to Central Bureau, the joint Australian-US Army codebreaking unit in Brisbane. Men like Jamieson (A.B. Jamieson, Nave’s second recruit) and (Athanasius) Treweek, who had cordial relations with the Americans, remained with FRUMEL throughout the war.
Fabian or his deputy John Lietweller were always in the office, 24 hours a day. Fabian was “a highly professional officer with an air of authority and a hint of Central European sophistication” although he was born in Butte, Montana in 1908. But he “regarded co-operation with anyone who was not in the US Navy or under its command as poor security”. One senior British officer said the atmosphere at FRUMEL was “What is yours is mine, and what is mine is my own”, and Fabian (backed by Redman) was not interested in any exchange of material with the Army’s Central Bureau. Once Fabian burnt a document in front of MacArthur's Intelligence Officer (G-2), Major General Charles A. Willoughby, to demonstrate that only MacArthur himself and Sutherland could be present at FRUMEL briefings and that Willoughby was not allowed to see it! 
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- Holmes, W. J. (1979). Double-edged Secrets: U.S. Naval Intelligence Operations in the Pacific During World War II. Annapolis, Maryland: Blue Jacket Books/Naval Institute Press. ISBN 1-55750-324-9.
- Jenkins, David (1992). Battle Surface! Japan's Submarine War Against Australia 1942–44. Milsons Point: Random House Australia. pp. 44–49, 157–159. ISBN 0-09-182638-1.
- Parker, Frederick D. "A Priceless Advantage: U.S. Navy Communications Intelligence and the Battles of Coral Sea, Midway, and the Aleutians". A Priceless Advantage: U.S. Navy Communications Intelligence and the Battles of Coral Sea, Midway, and the Aleutians. National Security Agency, Central Security Service. Retrieved November 20, 2006.
- Prados, John (1995). Combined Fleet Decoded: The Secret History of American Intelligence and the Japanese Navy in World War II. New York: Random House. ISBN 0-679-43701-0.
- "RAN/USN FLEET RADIO UNIT, MELBOURNE – FRUMEL". OZATWAR.com. 2006-03-25. Retrieved 2007-07-10.
- Smith, Michael: The Emperor’s Codes: Bletchley Park and the breaking of Japan’s secret ciphers (2000, Bantam London) ISBN 0-593-04642-0.
- Smith, Michael and Erskine, Ralph (editors): Action this Day (2001, Bantam London; pages 127–151) ISBN 0-593-04910-1 (Chapter 8: An Undervalued Effort: how the British broke Japan’s Codes by Michael Smith).