Station HYPO, also known as Fleet Radio Unit Pacific (FRUPAC) was the
United States Navysignals monitoring and cryptographic intelligence unit in Hawaiiduring World War II. It was one of two major Allied signals intelligence units in the Pacific theaters, along with FRUMELin Melbourne, Australia. [ [http://www.ibiblio.net/hyperwar////PTO/Magic/COMINT-CoralSea/PartOne.html Parker, Frederick D. "A Priceless Advantage: U.S. Navy Communications Intelligence and the Battles of Coral Sea, Midway, and the Aleutians". Fort Meade MD: Center for Cryptologic History, National Security Agency, 1993.] ] The station took its initial name from the phonetic code at the time for "H", as in "Hawaii". The precise importance and role of HYPO has been the subject of considerable controversy, reflecting internal tensions amongst US Navy cryptographic stations.
HYPO was under the control of the
OP-20-GNaval Intelligence section in Washington. It was located, prior to the attack on Pearl Harborof December 7, 1941, and for sometime afterwards, in the basement of the Old Administration Building at Pearl Harbor. Later on, a new building was constructed for the station, though it had been reorganized and renamed by then.
Cryptanalytic problems facing the United States in the Pacific prior to
World War IIwere largely those related to Japan. An early decision by OP-20-G in Washington divided responsibilities for them among CAST at Caviteand then Corregidor, in the Philippines, HYPO in Hawaii, and OP-20-G itself in Washington. Other Navy crypto stations, including Guam, Puget Sound, Bainbridge Islandwere tasked and staffed for signals interception and traffic analysis.
The US Army's
SISbroke into the highest level Japanese diplomatic cypher (called PURPLE by the US) well before the attack on Pearl Harbor. PURPLE produced little of military value, as the Japanese Foreign Ministrywas thought by the ultra-nationalists to be unreliable.Fact|date=August 2007 Furthermore, decrypts from PURPLE, eventually called MAGIC, were poorly distributed and used in Washington.Fact|date=August 2007 SIS was able to build several PURPLE machine equivalents. One was sent to CAST, but as HYPO's assigned responsibility did not include PURPLE traffic, no PURPLE machine was ever sent there. The absence of such a machine on site in Hawaii has long been seen by conspiracy theorists as a reason for US unpreparedness in Hawaii, and/or to be evidence of a conspiracy by high level officials to deprive Pearl Harbor of intelligence known to Washington. However, no uncontroverted hard evidence for any such conspiracy exists.
Japanese naval signals in 1941 & early 1942
HYPO was assigned responsibility for work on Japanese Navy systems, and after an agreement with
Australia, the United Kingdomand Netherlandsto share the effort, worked with crypto groups based at Melbourne, Hong Kongand Batavia. Prior to the attack on Pearl Harbor, the amount of available IJN traffic was low, and little progress had been made on the most important Japanese Navy system, called JN-25by U.S. analysts. JN-25 was used by th IJN for high level operations: movement and planning commands, for instance. It was a superencrypted code, eventually a two-book system, and was about the state-of-the-art at the time. Cryptanalytic progress was slow. Most references cite about 10% of messages partially (or sometimes completely) decrypted prior to 1 Dec 41, at which time a new edition of the system went into effect sending the cryptanalysts back to the beginning.
After the attack on Pearl Harbor, there was considerably more JN-25 traffic as the Japanese Navy operational tempo increased and geographically expanded, which helped progress against it. Hong Kong's contribution stopped until the crypto station there could be relocated (to
Ceylonand eventually Kenya), but HYPO and the Dutch at Batavia, in conjunction with CAST and OP-20-G made steady progress. HYPO in particular made significant contributions. Its people, including its commander, Joseph Rochefort, thought a forthcoming Japanese attack early in 1942 was intended for the central Pacific, while opinion at OP-20-G, backed by CAST, favored the North Pacific, perhaps in the Aleutians.
In early 1942, in response to the Japanese advances in the Philippines (which threatened CAST), the possibility of an invasion of Hawaii, and the increasing demand for intelligence, another signals intelligence center, known as NEGAT was formed in in Washington, using elements of OP-20-G. [ [http://www.ibiblio.net/hyperwar////PTO/Magic/COMINT-CoralSea/PartOne.html Parker, Frederick D. "A Priceless Advantage: U.S. Navy Communications Intelligence and the Battles of Coral Sea, Midway, and the Aleutians". Fort Meade MD: Center for Cryptologic History, National Security Agency, 1993.] ] In the words of NSA historian Frederick D. Parker:
:"By the middle of March 1942, two viable naval radio intelligence centers existed in the Pacific: one in Melbourne, Australia [FRUMEL] , and one, HYPO, in Pearl Harbor, Hawaii... The center on Corregidor (CAST) was no longer affiliated with a fleet command, and its collection and processing capabilities were rapidly disintegrating as a result of evacuations of personnel to Australia and destruction of its facilities by bombing and gunfire."
One of HYPO's personnel was responsible for the ruse which identified a call sign used in the Japanese traffic related to new offensive operation being planned. This involved a false claim of a fresh water shortage on Midway, broadcast in clear, which succeeded in evoking an encrypted Japanese response, noting that AF was reporting water troubles. Since AF was the apparent focus of the upcoming operation, it was clear that Midway would be the primary target.
As mid-1942 approached, HYPO was under high pressure, and there are tales of 36-hour stints, of Rochefort working in his bathrobe and appearing for briefings late and disheveled besides. This effort climaxed in the last week of May with the decryption of enough JN-25 traffic to understand the Japanese attack plan at Midway in some, but not complete, detail. This allowed Admiral Nimitz to gamble on the ambush which resulted in the
Battle of Midway, the loss of four Japanese carriers and many naval aviators, and what is generally agreed to have been the turning point of the Pacific War.
Post-Midway transfers and changes
After Midway, disputes between Rochefort, on behalf of HYPO, and OP-20-G in Washington, together with some bureaucratic infighting in Washington, resulted in the removal of Rochefort from command of his Hawaii command and eventually in his assignment to command a drydock on the West Coast. He did no further crypto work for the rest of the war; many writers have expressed astonishment at thus discarding one of the two or three most qualified Navy cryptographic and Japanese language experts. Nimitz, when he learned of Rochefort's treatment some years later, was quite displeased.
After having commandeered a girls' school in Washington (the Army took over one too), Naval Intelligence expanded greatly, as did OP-20-G, and HYPO became a smaller proportion of the total Navy signals intelligence effort in the Pacific.
* [http://www.navytv.org/channel.cfm?s=52&c=174 See a video interview with Donald M. Showers who was one of Rochefort's codebreaking team at Station HYPO in 1942]
Wikimedia Foundation. 2010.
Look at other dictionaries:
Station CAST — was the United States Navy signals monitoring and cryptographicintelligence 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 part of the Allied… … Wikipedia
Hypo — may be short for: * Hypoglycaemia, low blood glucose * Sodium hyposulfite, used in photographic processing * Hypodermic needle, syringe, or injection * Hypothecation * Hypo Real Estate, a German banking groupHYPO may refer to: * Station HYPO, a… … Wikipedia
Hypo-Haus — Hypo Turm, Hypo Hochhaus Hypo Haus im Januar 201 … Deutsch Wikipedia
Joseph Rochefort — Infobox Military Person name=Joseph John Rochefort born= 1898 died= death year and age|1976|1898 placeofbirth= placeofdeath= caption=Joseph J. Rochefort nickname= allegiance= United States of America branch= United States Navy serviceyears=1918… … Wikipedia
Signals intelligence in modern history — This article is a subset article of the article Signals intelligence, which addresses the unifying conceptual and technical factors and common technologies in this intelligence discipline. This article deals with signals intelligence in the… … Wikipedia
Central Bureau — The Central Bureau was one of two Allied Sigint organisations in the South West Pacific area (SWPA) during WWII. Central Bureau was attached to the HQ of the Allied Commander of the South West Pacific area, Douglas MacArthur. The other unit was… … Wikipedia
Battle of Midway — Part of the Pacific Theater of World War II … Wikipedia
World War II cryptography — Cryptography was used extensively during World War II, with a plethora of code and cipher systems fielded by the nations involved. In addition, the theoretical and practical aspects of cryptanalysis , or codebreaking , was much advanced. Probably … Wikipedia
OP-20-G — Active July 1, 1922 July 10, 1946 Allegiance United States Branch US Navy Type Code and Signal Section Role Signals intelligence … Wikipedia
Results of the attack on Pearl Harbor — The results of the attack on Pearl Harbor are many and significant. American responseOn December 7, 1941, the Japanese launched a surprise attack on Pearl Harbor and hastened the entry of the United States into World War II on the side of the… … Wikipedia