Everything about Joseph Rochefort totally explained
Captain
Joseph John Rochefort (
1898–
1976) was an American Naval officer and
cryptanalyst. His contributions and those of his team were pivotal to victory in the
Pacific War.
Significance
Rochefort was a major figure in the
U.S. Navy's cryptographic and intelligence operations from
1925 to
1946, except for a period after the
Battle of Midway, which his skills and effort helped win. Fluent in Japanese, he headed the Navy's fledgling cryptanalytic organization in the
1920s and provided cryptographic support to the U.S. Fleet. At the end of his Naval career (1942–1946), Rochefort successfully headed the Pacific Strategic Intelligence Group in Washington.
His significance lies not only in his great contributions, and those of his team, but in the fact that he and they stand for a monumental change, a sea change, in the nature of warfare in the first half of the 20th century. Just as
carriers replaced
battleships, so radio intelligence became a vital tool contributing to the success of commanders.
Early career
Rochefort enlisted in the Navy in
1918. He was commissioned as an ensign after graduation from the
Stevens Institute of Technology. Rochefort's tours ashore included cryptanalytic training under both Captain
Laurance Safford and the master codebreaker,
Agnes Meyer Driscoll, in
1925; a stint as second chief of the
Office of Naval Communications' newly created cryptanalytic organization,
OP-20-G, from 1926 to
1929; training in the
Japanese language from 1929 to 1932; and a two-year intelligence assignment in the
Eleventh Naval District,
San Diego, from 1936 to 1938. Until
1941, Rochefort spent nine years in cryptologic or intelligence-related assignments and fourteen years at sea with the U.S. Fleet in positions of increasing responsibility.
World War II -- Pearl
In early 1941, Laurance Safford, again chief of OP-20-G in Washington, sent Rochefort to
Hawaii to become Officer in Charge (OIC) of
Station Hypo in
Pearl Harbor. The reasons for Rochefort's appointment were obvious: he was an expert Japanese
linguist, an experienced and very talented
intelligence analyst, and a trained cryptanalyst. He by this time thoroughly understood the capabilities, and the limits, of radio interception of communications of enemy forces and what could be done with this information.
Rochefort handpicked many of HYPO's staff, and by the time of
Pearl Harbor, HYPO contained many of the Navy's best cryptanalysts, traffic analysts, and linguists, including
Thomas Dyer,
Wesley A. (Ham) Wright,
Joseph Finnegan, General
Alva Lasswell,
Thomas Huckins, and
Jack Williams.
Rochefort had a close working relationship and friendship with
Edwin T. Layton (later Rear Admiral Layton), whom he first met on the voyage to Tokyo to learn Japanese, which Layton was also undertaking at the Navy's request. Layton was in 1941 the chief intelligence officer for Admiral
Husband E. Kimmel, Commander of the Pacific Fleet. According to Layton's book, "A
nd I Was There: Pearl Harbor and Midway -- Breaking the Secrets" (1985), both he and Rochefort were denied access to decrypts of diplomatic messages sent in
Purple, the highest level diplomatic cypher, in the months before the Japanese attack. This was the result of a monopoly on intelligence which the Director of the War Plans Division,
Richmond K. Turner had achieved in Navy headquarters in Washington.
Rochefort and Layton, and their commander Admiral Kimmel, the men in the crosshairs, were kept in the dark. They were aware that negotiations with the Japanese were breaking down, and they'd even been issued a general "war warning" by Washington on 27 November, but they couldn't distinguish between deterioration and imminent threat, nor had they any reason to suspect an attack 4000 miles east of the Philippines, where both
MacArthur and the
US Asiatic Fleet were located. More importantly, they were in the dark about the fact that the spy whom Japan had sent to Honolulu,
Takeo Yoshikawa, was sending daily reports -- via the diplomatic messaging -- on the precise locations of ships in Pearl Harbor, using a grid system clearly meant as a precise aid to attacks by submarines and bombers (unlike other port and harbor information being transmitted to Tokyo from other parts of the world).
World War II -- After Pearl
After the Japanese attack, Navy cryptographers increased their attempts to break into highest level,
JN-25, Japanese Navy encrypted communications.
Station CAST (Cavite, in the Philippines),
Station HYPO (at Pearl Harbor; "H" for Hawaii),
OP-20-G in Washington (NEGAT, "N" for Navy Department), with assistance from both British cryptographers (in Hong Kong, later Singapore, later
Ceylon), and Dutch cryptographers (in the
Dutch East Indies), combined to break enough
JN-25 traffic to provide useful intelligence reports and assessments regarding Japanese force disposition and intentions in early 1942.
How much of this work was done by Station HYPO (in contrast to OP-20-G, CAST, or the British or Dutch) is still controversial, but it's clear that Station HYPO made major, and likely the most critical, contributions.
Station HYPO (ie, Rochefort) maintained that the coming Japanese attack would be in the Central Pacific, while OP-20-G (with support from Station CAST) insisted it would be elsewhere in the Pacific, probably the
Aleutian Islands., possibly
Port Moresby in
Papua New Guinea, or possibly even on the west coast of the United States. (See Layton, p. 421). OP-20-G, which had been restructured (Safford having been reassigned) under the command of officers not trained as cryptanalysts, also insisted that the attack was scheduled for mid-June, not late May or early June, as Rochefort maintained. Nimitz's superior in Washington, Admiral
Ernest King, was being advised by OP-20-G.
What was clear was that there was an "invasion force" associated with target site “
AF”, but where or what was AF was the subject of debate.
It was one of the Station HYPO staff,
Jasper Holmes (see Layton, p. 421), who had previous experience with Midway when as an engineer he'd studied the
Pan Am facility there, who had the idea of faking a water supply failure on Midway Island. He suggested using a cleartext emergency warning, provoking Japanese JN-25 traffic on the subject, thus testing whether Midway was a target or not. Rochefort took the idea to Layton who took it to Admiral
Nimitz (who had replaced Kimmel), and Nimitz approved it.
The Japanese took the bait. They broadcast instructions for the code group for the major attack point to load additional water desalinization equipment, thus proving Washington’s analysis wrong and confirming Rochefort’s analysis of where the attack would come -- Midway.. Layton notes that the instructions also “produced an unexpected bonus”. They revealed that the assault was to come before mid-June.
Washington still wasn't convinced, however. Actually, the disagreement with Washington as to the date of the attack stimulated Rochefort’s team to one of their finest efforts, perhaps topping even the brilliant ruse they used to determine that the target denomination, AF, was Midway. Layton refers to the date-time data in Japanese naval messages as being “superenciphered,” meaning that this data was encoded even before it was added to the
JN-25 cipher. When HYPO made their all-out effort to crack this, and prove Washington wrong, they started by searching the stacks of printouts and
punch cards for five-digit number sequences. Those they found were in low grade codes, a poor starting point, but a starting point.
Layton, pp. 427-8, goes on to say the the next task was to unravel the cipher itself. He credits Lieutenant
Joseph Finnegan, a linguist-cryptanalyst, as the person who "finally hit upon the method that the Japanese had used to lock up their date-time groups."
The method involved what he calls a 12 x 31 "garble check" --12 rows for months, 31 columns for day.
Thus: "To encipher, for example 27 May, one picked the 5th line (May=SO), ran across to the twenty-seventh column, HA, and recorded the kana at that intersection, HO. The encipherment, then, was SO, HA, HO, the third kana providing the garble check."
An intercept of 26 May with orders for two destroyer groups escorting invasion transports was analyzed with this table and “really clinched the pivotal date of the operation” as either 4 or 5 June.
During the month of May 1942, Rochefort and his group decrypted, translated, reviewed, analyzed, and reported as many as 140 messages per day. During the week before Nimitz issued his final orders, “decrypts were being processed at the rate of five hundred to a thousand a day.” Layton, pp. 422:
There are stories about Rochefort, in his bathrobe, doing 36 hour continuous shifts in Station HYPO's basement offices. Rochefort, in his oral history interview referenced below, says "I started to wear a smoking jacket over the uniform and I wore this darn thing because it had pockets in it and I could get my pipe and my pouch this way. Then my feet got sore. It was from the concrete floor we'd down there. That's all we'd -- a concrete floor. And my feet kept getting sore. So I started wearing slippers because the shoes hurt my feet." Layton also describes how, in the critical weeks of May, Rochefort installed a cot so that he could be on call at all times. Other team members also put in long hours, fighting fatigue “with Benzedrine tablets that were passed around like jellybeans,” according to Layton.
All this effort and talent, and all these ideas, enabled Admiral Nimitz -- enabled him to set up the ambush which led, due in great part to the brilliant effort of
Admiral Spruance and the heroism of his men, particularly the
torpedo squadrons, to victory and to what was the turning point of the Pacific War – six months after it had begun. See
Battle of Midway.
World War II -- After Midway
“The denouement of the Battle of Midway wasn't one of the U.S. Navy's finest hours.” So opens the discussion by Steven Budiansky (http://www.worldwar2history.info/Midway/intelligence.html) of the Navy's treatment of Rochefort after Midway.
When Nimitz forwarded to Admiral King the recommendation of Fourteenth Naval District command that Rochefort be awarded the Distinguished Service Medal, Rochefort, “with a keener measure of Washington politics than his commander”, said that it would only "make trouble."
But Washington, ie, the Redman brothers [Johnand Joseph], were now “claiming sole credit for the victory at Midway”, and arguing that units in combat areas can't be relied upon to do more that simply read enemy messages and perform “routine work necessary to keep abreast of minor changes in the cryptographic systems involved." The older brother, Captain Joseph R. Redman, now Director of Naval Communications, made the preposterous argument that Rochefort was merely an “ex-Japanese language student" who was "not technically trained in Naval Communications."
These assertions were accepted by Admiral King’s chief of staff, and King denied Rochefort his medal.
Budiansky continues:
punch cards and printouts demonstrate, was great, and it was necessary to avoid duplication of effort. There was also a need to ensure that all relevant intelligence data bearing on an issue was viewed and analyzed.
Rochefort was right.
Postwar
Rochefort died in 1976. In 1985, he was
posthumously awarded the
Distinguished Service Medal. In 1986, he posthumously received the
Presidential Medal of Freedom, the highest military award during peacetime, for his cryptographic work in the period before the Battle of Midway. In 2000, he was inducted into the
National Security Agency,
Central Security Service Hall of Fame.
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