By Captain Duane L. Whitlock, U.S. Navy, Retired

On 26 May 1942, “it was estimated that 60 percent of Imperial Navy traffic was being intercepted (by the U.S. Navy) and 40 percent read, although the content recovered from the typical message averaged only about 10-15 percent.” [20] Obviously one does not get much intelligence out of a fifty-word message if only perhaps eight of the words can be read. Although the ability to read Japanese naval messages was expanding rapidly just before the battle of Midway, that less than fifty of the 280 ships later acknowledged to have been present were ever mentioned in JN-25 decrypts points to a subtle limitation as to what intelligence can be derived through cryptanalysts.

Throughout the entire war, the Japanese navy never attempted to disseminate a complete operation order by radio; apparently, as in the U.S. Navy, such orders were always delivered by hand. While JN-25 partial decrypts relating to the battles of the Coral Sea and Midway made tantalizing reference to operation orders and to such task organizations as the “striking force,” “assault force,” “Moresby force,” etc., the composition of these groups had to be deduced almost exclusively from traffic analysis.

In fact at the outset of the war, traffic analysis was, as it had been for many years, the only source of current intelligence bearing upon the strategic posture and the disposition of the surface, subsurface, and air elements of the Japanese navy. As cryptanalysts began to catch up with current events in 1942, it started to add to the traffic analysis picture the timely and precise details essential to achieving tactical advantage. The shooting down of Admiral Isoroku Yamamoto on 18 April 1943 is a classic example. [21] However, as has not been well understood by historians who have highlighted the many tactical successes, cryptanalysts made a rather limited contribution to “the big picture” in the “silent war” against the Japanese navy. Had it not been for the considerable number of victories mutually achieved by these two analytical methods in the silent war, the shooting war in the Pacific would have taken a far different and much more painful course.

Depiction of the shootdown of Admiral Isoroku Yamamoto

A vital point that should not be overlooked by historians and students of the war with Japan is the fact that something more than twenty years was required to bring on-line the radio intelligence organization that ultimately gave commanders what was perhaps the greatest strategic and tactical advantage in the history of naval warfare. That advantage shortened the war immeasurably, saved many lives, and reduced substantially the material and financial burden imposed upon American taxpayers. That such an organization ever came into existence stands as a monument to the foresight of two or three flag officers, not the least of them Admiral Upham, as previously noted, and also, at a much earlier date, Commander Battleship Force, U.S. Pacific Fleet, who in a letter of 16 May 1921 to CNO recommended that “all rated radiomen be given sufficient instruction in receiving Japanese Language Code to at least be able to recognize it when copied.” [22]

The latter recommendation is likely to have come to naught were it not for the singular initiative, imagination, persistence, and ingenuity applied to it by Lieutenant Laurance F. Safford. One of the first U.S. naval officers to specialize in the new field of cryptology, he was largely responsible for introducing the art of cryptanalysts into the Navy. Heading the newly established Cryptographic Research Desk in the CNO staff (or OPNAV) Code and Signal Section in 1924-1925, he spearheaded the Navy’s attack against the Japanese diplomatic codes, provided rudimentary training in cryptanalysts to one or two specially elected junior officers, encouraged the ad hoc Marine Corps and Navy intercept efforts taking place in the Asiatic Fleet, and took steps to design and acquire the special Japanese typewriters needed to enhance these and the more formal intercept operations yet to come.

Those accomplishments in turn anticipated the contributions to be made through the technical and analytical skills of carefully selected Navy radiomen. The special training needed to convert these radiomen into full-fledged intercept operators was largely devised by the radiomen themselves, and in this regard the accomplishment of Chief Radioman Harry Kidder was at least as significant as that of Lieutenant Safford. Furthermore, without the incentive provided by the enlisted analysts on Guam in 1930, the special effort to test the intelligence potential of traffic analysis might not have come to pass in 1933. It was in this test that Lieutenant Joseph Wenger proved that traffic analysis is a unique source of special intelligence. He was the father of traffic analysis in the Navy, in much the same sense that Lieutenant Safford was the father of cryptanalysts.

Lieutenant Laurance F. Safford,
father of Cryptanalysts
Lieutenant Joseph Wenger
Father of Traffic Analysis

Remarkably, this protracted development effort had its genesis in the era of “downsizing” that followed World War I, when the allocation of such Navy funds as were available all but ignored the needs of intelligence. Then too, the pronouncement in 1929 by the Secretary of State, Henry L. Stimson, that “gentlemen do not read each other’s mail” tended to place any monies openly programmed for that purpose in a very unfavorable light. Had the Navy Department allowed Stimson’s ultimatum to blunt the efforts of the visionaries noted above, there would have been no Navy radio intelligence organization, no victory in the Coral Sea or at Midway, and perhaps no decisive victory anywhere else. In the present era, one can but hope that strategic and tactical intelligence needs will never again be allowed to hang by such a slender thread. Budgetary planners, both military and civilian, need to realize that the next shooting war could well be lost if the silent war has not been won in peacetime.


20. John Winton, Ultra in the Pacific: How Breaking Japanese Codes and Ciphers Affected Naval Operations against Japan, 1941-45 (Annapolis, Md.: U.S. Naval Institute Press, 1994). Back

21. Layton, p. 474. Back

22. Holtwick, SRH-355, p. 39. Back

Captain Duane L. Whitlock, USN
On-The-Roof Gang Class #20
1917 – April 10, 2007

Captain Whitlock entered the service in June 1935, became a radioman, and was specially trained to intercept Japanese naval radio communications. He served as an intercept operator in Hawaii and on Guam, became a self-trained analyst in 1940 while stationed in the Philippines, and began producing intelligence estimates on the Japanese navy’s air, surface, and subsurface operations. Evacuated from Corregidor in March 1942, he continued to produce intelligence on the Japanese navy throughout the war, first from Australia and then from Washington, D.C. Commissioned temporarily in 1943, he received a permanent commission after the war, attended George Washington University, and served the rest of his career in the naval cryptologic and intelligence communities. After attending the Naval War College in 1958, he served as a cryptologic advisor on the staff of the Commander in Chief, Pacific Fleet. Retired since 1967, he is the author of Critical Thoughts and Notions (Danville, Calif.: Omega, 1988).

This article is adapted from a paper delivered on 11 August 1994 to a conference on “World War II in the Pacific” at Crystal City, Virginia, cosponsored by the Naval Historical Center, U.S. Naval Institute, Naval Order of the United States, Naval Historical Foundation, Marine Corps Association, American Society of Naval Engineers, and Marine Corps Historical Foundation.

Source: Naval War College Review, Vol. 48, No. 4 (AUTUMN 1995)