The Battle of Midway Roundtable
Reading Yamamoto’s Mail
RADM D. M. “Mac” Showers, USN-Retired
by Ronald Russell
Updated 29 August 2009
(The following originally appeared in Veterans Biographies, distributed during the annual Battle of Midway commemoration in San Francisco, June 2006)
In August 1940 Mac Showers joined the Naval Reserve while in his senior year at the University of Iowa, where he majored in journalism and political science. He was commissioned as a USNR ensign in September 1941 and commenced active duty with the 13th Naval District headquarters (Com 13) in Seattle. At Com 13 he was introduced to the world of naval intelligence while a member of the district intelligence officer’s staff.
In February 1942 he was transferred to Pearl Harbor and to the staff of Commander Joseph Rochefort, who was to become one of primary architects for the stunning victory at Midway. Rochefort was in charge of the Combat Intelligence Unit at Pearl, known generally in the history books as “Station HYPO.” HYPO was tasked with breaking the Japanese navy’s radio code, analyzing the intelligence derived, and providing CINCPAC (Admiral Nimitz and his staff) with the best possible view of the enemy’s battle plans. Rochefort was a master of the art, and under his supervision the cryptanalysts at HYPO ultimately divined virtually the entire Japanese operations order for Midway before the battle commenced. Ensign Showers was an intelligence analyst working closely with the unit’s cryptanalysts and Japanese linguists.
He was specifically responsible for extracting key data from each intercept, plotting the movements of the Japanese ships en route to Midway, and preparing graphic presentations of such movements for delivery to CINCPAC.
The remarkable success of the HYPO team, with support from a similar operation in Australia, was the fundamental key to the “Miracle at Midway.” As it turned out, the quality of the intelligence delivered to CINCPAC by Ensign Showers and his comrades was nearly perfect—Admiral Nimitz stated after the battle that with regard to the initial Japanese air strike on the atoll, his staff’s prediction for its arrival had been off by only five minutes on the clock and five degrees on the compass!
Mac Showers remained a fleet intelligence specialist throughout the war, after which he transferred to the regular Navy. He retired in 1972 and commenced a second career with the Central Intelligence Agency, where he served until 1983. In 1986 he was instrumental in securing a posthumous Distinguished Service Medal for Joseph Rochefort, who had received no awards for his vital achievements at HYPO in 1942.
Photos of Mac Showers
Navy Cryptology at the Battle of Midway: Our Finest Hour (More about the communications intelligence victory at Midway, by Phil Jacobsen)
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