Double-edged Secretsi U.s. Naval Intelligence Operations In The Pacific During World War Ii

August 2017

by W. J. Holmes Naval Institute Press 35 photographs and maps 231 pages, $11.95

The story of breaking the World War II Japanese code has been told before, but never from the inside. Holmes, a retired Navy captain, spent the war in the naval intelligence center—Fleet Radio Unit, Pacific or FRUPac—at Pearl Harbor, and he tells about the baffling task of that most unmilitary office as only a participant could.

Navy cryptanalysts, hidden away in a basement with their complex machines and masses of disparate data, sweated over their seemingly impenetrable puzzles or sometimes simply played hunches. Their sources included weather reports, documents salvaged from a sunken enemy submarine, even a count of privies on an enemy-held island. Again and again, when they had succeeded in breaking part of a code, it would suddenly be changed, “like blowing out a candle,” Holmes says, leaving FRUPac to start all over again.

Although proud of FRUPac’s contribution, the author feels that we paid a high price to keep the Japanese from learning that we had penetrated their communications. Often we deliberately failed to act on what we knew. Holmes still grieves that hundreds of American lives were lost by this policy. “Secrecy is a double-edged weapon,” he concludes, “and it sometimes inflicts deeper wounds on its wielder than upon his opponents.”