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50-661: HYPO was under the control of the OP-20-G Naval Intelligence section in Washington. Before the attack on Pearl Harbor of December 7, 1941, and for some time afterwards, HYPO was 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

100-627: 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

150-705: A lieutenant commander if over 35). But control was by "regular military types". The Navy wanted the Army to forbid civilians to touch the SIGABA cipher machine like the Navy; though it was developed by a civilian ( William Friedman ). A Royal Navy visitor and intercept specialist Commander Sandwith reported in 1942 on "the dislike of Jews prevalent in the US Navy (while) nearly all the leading Army cryptographers are Jews". In 1940, SIS and OP-20-G came to agreement with guide lines for handling MAGIC;

200-513: A lieutenant commander if over 35). But control was by "regular military types". The Navy wanted the Army to forbid civilians to touch the SIGABA cipher machine like the Navy; though it was developed by a civilian ( William Friedman ). A Royal Navy visitor and intercept specialist Commander Sandwith reported in 1942 on "the dislike of Jews prevalent in the US Navy (while) nearly all the leading Army cryptographers are Jews". In 1940, SIS and OP-20-G came to agreement with guide lines for handling MAGIC;

250-443: A result of evacuations of personnel to Australia and destruction of its facilities by bombing and gunfire. Japanese traffic was intercepted regarding a new offensive operation being planned against a target only identified as AF. LCDR Wilfred J. Holmes at HYPO was responsible for the ruse which identified AF: a false report of a fresh water shortage on Midway was radioed in clear , evoking an encrypted Japanese response noting that AF

300-714: The Army agreed that they would supply the White House in January, March, May, July, September and November and the Navy in February, April, June, August, October and December. But in May 1941 MAGIC documents were found in the desk of Roosevelt's military aide Edwin "Pa" Watson and the Navy took over; while the Army provided MAGIC to the State Department instead. The result was that much of the MAGIC

350-406: The Army agreed that they would supply the White House in January, March, May, July, September and November and the Navy in February, April, June, August, October and December. But in May 1941 MAGIC documents were found in the desk of Roosevelt's military aide Edwin "Pa" Watson and the Navy took over; while the Army provided MAGIC to the State Department instead. The result was that much of the MAGIC

400-506: The Army was responsible on even-numbered days and the Navy on odd-numbered days. So, on the first minute after midnight on 6 December 1941 the Navy took over. But USN Lt-Comdr Alwin Kramer had no relief officer (unlike the Army, with Dusenbury and Bratton); and that night was being driven around by his wife. He was also responsible for distributing MAGIC information to the President; in January 1941

450-405: The Army was responsible on even-numbered days and the Navy on odd-numbered days. So, on the first minute after midnight on 6 December 1941 the Navy took over. But USN Lt-Comdr Alwin Kramer had no relief officer (unlike the Army, with Dusenbury and Bratton); and that night was being driven around by his wife. He was also responsible for distributing MAGIC information to the President; in January 1941

500-410: The Army's SIS but Commander Joseph Wenger had picked out the "perfect new home" for the rapidly expanding OP-20-G and commandeered a private girls' school Mount Vernon College for Women for $ 800,000 (a fraction of what the buildings and grounds were worth), in 1944, compensated $ 1.038 million. So on 7 February 1943 it opened at what was called the "Naval Communications Annex", and staff moved in over

550-410: The Army's SIS but Commander Joseph Wenger had picked out the "perfect new home" for the rapidly expanding OP-20-G and commandeered a private girls' school Mount Vernon College for Women for $ 800,000 (a fraction of what the buildings and grounds were worth), in 1944, compensated $ 1.038 million. So on 7 February 1943 it opened at what was called the "Naval Communications Annex", and staff moved in over

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600-571: The Division of Naval Communications (DNC), as Op-20-G, on July 1, 1922. In January 1924, a 34-year-old U.S. Navy lieutenant named Laurance F. Safford was assigned to expand OP-20-G's domain to radio interception. He worked out of Room 2646, on the top floor of the Navy Department building in Washington, D.C. Japan was of course a prime target for radio interception and cryptanalysis , but there

650-411: The Division of Naval Communications (DNC), as Op-20-G, on July 1, 1922. In January 1924, a 34-year-old U.S. Navy lieutenant named Laurance F. Safford was assigned to expand OP-20-G's domain to radio interception. He worked out of Room 2646, on the top floor of the Navy Department building in Washington, D.C. Japan was of course a prime target for radio interception and cryptanalysis , but there

700-714: The Japanese bombs had smashed the US Navy 's fleet at anchor in Pearl Harbor . In February 1942 power struggles within the Navy resulted in the sidelining of Laurance Safford , with the support of Admirals Ernest King and Richmond K. Turner (and Joseph Redman ) for the centralizing of control of naval intercept and codebreaking in Washington. So two new sections were headed by John R. Redman (Communications Combat Intelligence section) and Joseph Wenger (Communications Cryptanalytical section; to handle decryption and translation). Safford

750-560: The Japanese bombs had smashed the US Navy 's fleet at anchor in Pearl Harbor . In February 1942 power struggles within the Navy resulted in the sidelining of Laurance Safford , with the support of Admirals Ernest King and Richmond K. Turner (and Joseph Redman ) for the centralizing of control of naval intercept and codebreaking in Washington. So two new sections were headed by John R. Redman (Communications Combat Intelligence section) and Joseph Wenger (Communications Cryptanalytical section; to handle decryption and translation). Safford

800-646: The Pacific prior to World War II were largely those related to Japan . An early decision by OP-20-G in Washington divided responsibilities for them among CAST at Cavite and then Corregidor , in the Philippines , HYPO in Hawaii, and OP-20-G itself in Washington. Other Navy crypto stations, including Guam and Bainbridge Island on Puget Sound were tasked and staffed for signals interception and traffic analysis . The US Army's Signals Intelligence Service (SIS) broke into

850-549: The Pacific. OP-20-G OP-20-G or "Office of Chief Of Naval Operations ( OP NAV), 20 th 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 was to intercept, decrypt, and analyze naval communications from Japanese , German , and Italian navies. In addition OP-20-G also copied diplomatic messages of many foreign governments. The majority of

900-658: The US Secretary of State, Cordell Hull , at 1:00 PM Washington time that negotiations between the United States and Japan were ended. The embassy was then to destroy their cipher machines. This sounded like war, and although the message said nothing about any specific military action, Kramer also realized that the sun would be rising over the expanses of the central and western Pacific by that time. The two men both tried to get in touch with Army Chief of Staff General George C. Marshall . After some agonizing delays, Marshall got

950-548: The US Secretary of State, Cordell Hull , at 1:00 PM Washington time that negotiations between the United States and Japan were ended. The embassy was then to destroy their cipher machines. This sounded like war, and although the message said nothing about any specific military action, Kramer also realized that the sun would be rising over the expanses of the central and western Pacific by that time. The two men both tried to get in touch with Army Chief of Staff General George C. Marshall . After some agonizing delays, Marshall got

1000-572: The ambush that resulted in the Battle of Midway , the loss of four Japanese carriers and many naval aviators for much lower Allied losses, and what is generally agreed to have been the turning point of the Pacific War. In October 1942, after Midway, power struggles within the Navy resulted in the sidelining of Laurance Safford , with the support of Admirals Ernest King and Richmond K. Turner (and Joseph Redman ). Control of naval intercept and codebreaking

1050-479: The art of reading kana transmissions when the Navy began conducting classes in the subject in 1928. The classes were conducted by the Room 2426 crew, and the radiotelegraph operators became known as the "On-The-Roof Gang". By June 1940, OP-20-G included 147 officers, enlisted men, and civilians, linked into a network of radio listening posts as far-flung as the Army's. OP-20-G did some work on Japanese diplomatic codes, but

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1100-432: The art of reading kana transmissions when the Navy began conducting classes in the subject in 1928. The classes were conducted by the Room 2426 crew, and the radiotelegraph operators became known as the "On-The-Roof Gang". By June 1940, OP-20-G included 147 officers, enlisted men, and civilians, linked into a network of radio listening posts as far-flung as the Army's. OP-20-G did some work on Japanese diplomatic codes, but

1150-416: The decrypts and methodically examined them. He realized their importance and sent a warning to field commanders, including Major General Walter Short , the Army commander in Hawaii. However, Marshall was reluctant to use the telephone because he knew that telephone scramblers weren't very secure and sent it by less direct channels. Due to various constraints and bumblings, Short got the message many hours after

1200-416: The decrypts and methodically examined them. He realized their importance and sent a warning to field commanders, including Major General Walter Short , the Army commander in Hawaii. However, Marshall was reluctant to use the telephone because he knew that telephone scramblers weren't very secure and sent it by less direct channels. Due to various constraints and bumblings, Short got the message many hours after

1250-531: 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 Ministry was thought by the ultra-nationalists to be unreliable. Furthermore, decrypts from PURPLE, eventually called MAGIC , were poorly distributed and used in Washington. SIS was able to build several PURPLE machine equivalents. One

1300-529: The limit of the percent of the messages that were decrypted at 10%, they were not privy to the latest information. Wilford in his Decoding Pearl Harbor: USN Cryptanalysis and the Challenge of JN-25B in 1941, suggests that this view is now untenable and that the JN-25 codes were readable to a great extent and hence, lends "support to the revisionist theories of Toland and Stinnett". After the attack on Pearl Harbor, there

1350-514: The next two months. Station NEGAT OP-20-G or "Office of Chief Of Naval Operations ( OP NAV), 20 th 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 was to intercept, decrypt, and analyze naval communications from Japanese , German , and Italian navies. In addition OP-20-G also copied diplomatic messages of many foreign governments. The majority of

1400-693: The organization's primary focus was on Japanese military codes. The US Navy first got a handle on Japanese naval codes in 1922, when Navy agents broke into the Japanese consulate in New York City , cracked the safe, took photographs of pages of a Japanese navy codebook, and left, having put everything back as they had found it. Before the war, the Navy cipher bureau operated out of three main bases: The US Army Signal Intelligence Service (SIS) and OP-20-G were hobbled by bureaucracy and rivalry, competing with each other to provide their intelligence data, codenamed " MAGIC ", to high officials. Complicating matters

1450-638: The organization's primary focus was on Japanese military codes. The US Navy first got a handle on Japanese naval codes in 1922, when Navy agents broke into the Japanese consulate in New York City , cracked the safe, took photographs of pages of a Japanese navy codebook, and left, having put everything back as they had found it. Before the war, the Navy cipher bureau operated out of three main bases: The US Army Signal Intelligence Service (SIS) and OP-20-G were hobbled by bureaucracy and rivalry, competing with each other to provide their intelligence data, codenamed " MAGIC ", to high officials. Complicating matters

1500-450: The section's effort was directed towards Japan and included breaking the early Japanese "Blue" book fleet code . This was made possible by intercept and High Frequency Direction Finder (HFDF) sites in the Pacific , Atlantic , and continental U.S., as well as a Japanese telegraphic code school for radio operators in Washington, D.C. The Code and Signal Section was formally made a part of

1550-401: The section's effort was directed towards Japan and included breaking the early Japanese "Blue" book fleet code . This was made possible by intercept and High Frequency Direction Finder (HFDF) sites in the Pacific , Atlantic , and continental U.S., as well as a Japanese telegraphic code school for radio operators in Washington, D.C. The Code and Signal Section was formally made a part of

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1600-547: Was Joseph Rochefort in Hawaii (he was assigned to command a dry-dock on the West Coast). After Midway, Rochefort was recommended for the Distinguished Service Medal to Admiral Ernest King . However, personal enmity from his chief of staff due to a prior passing encounter, and non-support from his immediate supervisors, led King to deny the award. Nimitz, when he learned of Rochefort's treatment some years later,

1650-493: Was assigned responsibility for work on Japanese Navy systems, and after an agreement with Australia , the United Kingdom and Netherlands to share the effort, worked with crypto groups based at Melbourne , Hong Kong and 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-25 by U.S. analysts. JN-25

1700-456: Was centralizing in OP-20-G in Washington, where two new sections were headed by John R. Redman (Communications Combat Intelligence section) and Joseph Wenger (Communications Cryptanalytical section; to handle decryption and translation). Safford was shifted to an administrative support and cryptographic research role; so was sidelined for the remainder of the war (doing no further crypto work); as

1750-582: 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 Ceylon and 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

1800-426: Was delayed or unused. There was no efficient process for assessing and organizing the intelligence, as was provided postwar by a single intelligence agency. In the early hours of the morning of 7 December 1941, the U.S. Navy communications intercept station at Fort Ward on Bainbridge Island, Washington , picked up a radio message being sent by the Japanese government to the Japanese embassy in Washington, D.C. It

1850-426: Was delayed or unused. There was no efficient process for assessing and organizing the intelligence, as was provided postwar by a single intelligence agency. In the early hours of the morning of 7 December 1941, the U.S. Navy communications intercept station at Fort Ward on Bainbridge Island, Washington , picked up a radio message being sent by the Japanese government to the Japanese embassy in Washington, D.C. It

1900-607: Was formed in Washington, using elements of OP-20-G. 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

1950-429: Was quite displeased. Rochefort was posthumously awarded the medal after a campaign by his intelligence officers galvanized Admiral D. "Mac" Showers and eventually CIA head William Casey to rectify the oversight. Having commandeered a girls' school in Washington (the Army took over one too), Naval Intelligence and OP-20-G expanded greatly. HYPO became a smaller proportion of the total Navy signals intelligence effort in

2000-452: Was reporting water troubles; AF had to be Midway. 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

2050-452: 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 hard evidence for any such conspiracy exists. HYPO

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2100-406: Was shifted to an administrative support and cryptographic research role; thus was sidelined for the remainder of the war, as ultimately was Joseph Rochefort in Hawaii. With Japanese advances in the Philippines , a possible invasion of Hawaii, and greater demand for intelligence, OP-20-G undertook two courses of action: In Summer 1942 the Navy went through the motions of perhaps co-locating with

2150-406: Was shifted to an administrative support and cryptographic research role; thus was sidelined for the remainder of the war, as ultimately was Joseph Rochefort in Hawaii. With Japanese advances in the Philippines , a possible invasion of Hawaii, and greater demand for intelligence, OP-20-G undertook two courses of action: In Summer 1942 the Navy went through the motions of perhaps co-locating with

2200-546: Was that the Coast Guard , the FBI , and even the FCC also had radio-intercept operations. The Navy organization at OP-20-G was more conventionally hierarchical than the Army at Arlington Hall which went more on merit rather than rank (like Bletchley Park), though commissions were handed out to "civilians in uniform" with rank according to age (an ensign for 28 or under, a lieutenant to 35 or

2250-403: Was that the Coast Guard , the FBI , and even the FCC also had radio-intercept operations. The Navy organization at OP-20-G was more conventionally hierarchical than the Army at Arlington Hall which went more on merit rather than rank (like Bletchley Park), though commissions were handed out to "civilians in uniform" with rank according to age (an ensign for 28 or under, a lieutenant to 35 or

2300-482: Was the last in a series of 14 messages that had been sent over the previous 18 hours. The messages were decrypted by a PURPLE analogue machine at OP-20-G and passed to the SIS for translation from Japanese, early on the morning of December 7. Army Colonel Rufus S. Bratton and Navy Lieutenant Commander Alwin Kramer independently inspected the decrypts. The decrypts instructed the Japanese ambassador to Washington to inform

2350-436: Was the last in a series of 14 messages that had been sent over the previous 18 hours. The messages were decrypted by a PURPLE analogue machine at OP-20-G and passed to the SIS for translation from Japanese, early on the morning of December 7. Army Colonel Rufus S. Bratton and Navy Lieutenant Commander Alwin Kramer independently inspected the decrypts. The decrypts instructed the Japanese ambassador to Washington to inform

2400-587: Was the problem of finding personnel who could speak Japanese . The Navy had a number of officers who had served in a diplomatic capacity in Japan and could speak Japanese fluently, but there was a shortage of radiotelegraph operators who could read Japanese Wabun code communications sent in kana . Fortunately, a number of US Navy and Marine radiotelegraph operators operating in the Pacific had formed an informal group in 1923 to compare notes on Japanese kana transmissions. Four of these men became instructors in

2450-539: Was the problem of finding personnel who could speak Japanese . The Navy had a number of officers who had served in a diplomatic capacity in Japan and could speak Japanese fluently, but there was a shortage of radiotelegraph operators who could read Japanese Wabun code communications sent in kana . Fortunately, a number of US Navy and Marine radiotelegraph operators operating in the Pacific had formed an informal group in 1923 to compare notes on Japanese kana transmissions. Four of these men became instructors in

2500-505: Was used by the IJN for high level operations: movement and planning commands, for instance. It was a state-of-the-art superencrypted code , eventually a two-book system. Cryptanalytic progress was slow. Most references cite about 10% of messages partially (or sometimes completely) decrypted prior to December 1, 1941, at which time a new version of the system went into effect, requiring the cryptanalysts to start again. Although most references did set

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