Fleet Radio Units (FRU) were the major centers for Allied cryptological and

signals intelligence Signals intelligence (SIGINT) is the act and field of intelligence-gathering by interception of ''signals'', whether communications between people (communications intelligence—abbreviated to COMINT) or from electronic signals not directly u ...

during the Pacific Campaign of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. Initially two FRUs were established in the Pacific, one at

Pearl Harbor Pearl Harbor is an American lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It was often visited by the naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the Reci ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

, called

Station HYPO Station HYPO, also known as Fleet Radio Unit Pacific (FRUPAC), was the United States Navy signals monitoring and cryptographic intelligence unit in Hawaii during World War II. It was one of two major Allied signals intelligence units, called Fl ...

or FRUPAC (Fleet Radio Unit, Pacific), and the other, called

Station CAST Station CAST was the United States Navy signals monitoring and cryptographic intelligence fleet radio unit at Cavite Navy Yard in the Philippines, until Cavite was captured by the Japanese forces in 1942, during World War II. It was an important ...

or Belconnen, at Cavite Naval Yard, then

Corregidor Corregidor (, , ) is an island located at the entrance of Manila Bay in the southwestern part of Luzon in the Philippines, and is considered part of Cavite City and thus the province of Cavite. It is located west of Manila, the nation's capi ...

, Philippines. With the fall of the Philippines to

Imperial Japanese The Empire of Japan, also known as the Japanese Empire or Imperial Japan, was the Japanese nation state that existed from the Meiji Restoration on January 3, 1868, until the Constitution of Japan took effect on May 3, 1947. From 1910 to 19 ...

forces in April and May 1942, CAST personnel were evacuated to a newly established FRU at

Melbourne, Australia Melbourne ( , ; Boonwurrung/ or ) is the capital and most populous city of the Australian state of Victoria, and the second most-populous city in Australia, after Sydney. The city's name generally refers to a metropolitan area also known ...

, called FRUMEL (Fleet Radio Unit, Melbourne). HYPO and FRUMEL supervised detached field units scattered at various locations and aboard ships throughout the south, central, and north Pacific areas until the end of World War II. A third center, NEGAT, was based at

OP-20-G OP-20-G or "Office of Chief Of Naval Operations (OPNAV), 20th Division of the Office of Naval Communications, G Section / Communications Security", was the U.S. Navy's signals intelligence and cryptanalysis group during World War II. Its mission ...

headquarters in

Washington DC Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and Federal district of the United States, federal district of the United States. The city is on the Potomac River, across from ...

. The entire cryptanalysis effort conducted by the units was called '' Operation Magic''. Liaison between the units and with the

Far East Combined Bureau The Far East Combined Bureau, an outstation of the British Government Code and Cypher School, was set up in Hong Kong in March 1935, to monitor Japanese, and also Chinese and Russian (Soviet) intelligence and radio traffic. Later it moved to Sing ...

(FECB; the British signals intelligence center at

Colombo Colombo, ( ; , ; , ), is the executive and judicial capital and largest city of Sri Lanka by population. The Colombo metropolitan area is estimated to have a population of 5.6 million, and 752,993 within the municipal limits. It is the ...

Ceylon Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

in 1942) was titled '' Copek''.

References

* * * * *{{cite book , last = Willmott , first = H. P. , authorlink = , year = 1983 , chapter = , title = The Barrier and the Javelin: Japanese and Allied Pacific Strategies February to June 1942 , publisher = Naval Institute Press , location = Annapolis, Maryland , isbn = 0-87021-535-3 , url-access = registration , url = https://archive.org/details/empiresinbalance00will Military units and formations of Australia in World War II History of Australia (1901–1945) Australian intelligence agencies Signals intelligence agencies of World War II History of cryptography Cryptography organizations Locations in the history of espionage Pacific War