Donald McCollister Showers was born August 25, 1919 in Iowa City, Iowa, the son of Charles N. Showers (1888- 1973) and Hedwig Marie Potratz (1889 -1980).  He preferred to be called “Mac,” an abbreviation of his middle name, McCollister, his paternal grandmother’s maiden name.
Mac graduated from the State University of Iowa with a B.A. and certificate in journalism.  His interest in the Navy led him to enroll in Naval Reserve Midshipman’s School in Chicago at Northwestern University in the Navy’s fast track V-7 program.

Mac was commissioned an ensign on September 12, 1941.  Trained in counterintelligence (CI), he reported for duty at the District Intelligence Office (DIO) in Honolulu, Hawaii.  But DIO needed experienced investigators, so in February 1942 he was reassigned to the Combat Intelligence Unit, Station HYPO, Pearl Harbor, Hawaii commanded by CDR Joseph Rochefort (1900-1976).

Although he had no background in intelligence or code breaking, Mac quickly integrated himself to the mission of HYPO, which was to break the Japanese Naval code, JN-25.  This was critical to provide ADM Chester Nimitz with the intelligence he needed to best position his force for coming battles in order to achieve supremacy against the Japanese Navy at the Battle of Midway in June 1942 and other engagements.

After Rochefort left HYPO in the summer of 1942, Mac remained, serving under Rochefort’s relief, CDR William Googgins (1898-1985).  Mac played an important role in the 1943 shoot down of the airplane carrying Japanese ADM Isoroku Yamamoto.  When Yamamoto’s itinerary was intercepted, Mac analyzed it to determine if it was a plausible schedule or not.  It was, and his analysis led, in part, to the decision to target Yamamoto.

In 1944, Mac was selected to serve as deputy to CAPT Edwin Layton (1903-1984), ADM Nimitz’s intelligence officer, to establish a fleet combat intelligence center (Advance Intelligence Center) on Guam.  While at Guam AIC, he gave daily intelligence briefs and provided intelligence to the planners of the invasion of Japan. In October 1946, Mac became one of the first naval officers to be designated an intelligence specialist.

On June 12, 1948, he married Sarah Vivian “Billie” Gilliland (1923-2002).  They had a daughter and two sons.

In 1965, Mac was selected for Rear Admiral, thus becoming the only member of HYPO to attain flag rank.  During the Vietnam War, he was assigned as the Fleet Intelligence Officer to the Command in Chief of the Pacific Fleet, an assignment that CAPT Layton had previously held.

His last assignment while serving in the Navy was a Chief of Staff at the Defense Intelligence Agency (DIA).  While at DIA, RADM Showers was charged with heading an effort, called PURPLE DRAGON, to find and correct breaches of security which had become known to the North Vietnamese during the Vietnam War.  Its findings led to greater combat effectiveness and saved lives in Vietnam, and its lessons are applied in all military planning to this very day.  This program is called operations security (OPSEC).

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Admiral Showers retired from the navy on December 31, 1971.  During his career, he had been awarded the Navy Distinguished Service Medal, the Legion of Merit and the Bronze Star. Three days after retiring from the Navy, he embarked on a civilian career with the Central Intelligence Agency.  In the early 1980s, he served as special assistant to CIA Director William Casey (1913-1987). After 12 years with the CIA, he retired a second time in order to become a full-time caregiver to his wife, Billie, who was diagnosed with Alzheimer’s disease.  Billie died in 2002. After his retirement from CIA Admiral Showers continued to lead an active life.  He was helped to fund raise to find a cure for Alzheimer’s .  He traveled and spoke to groups, both civilian and military, about his experience at HYPO.

Admiral Showers was central to the effort to honor CAPT Rochefort’s efforts at HYPO.  Admiral Nimitz had nominated CAPT Rochefort for the Navy Distinguished Service Medal (DSM), but it had been disapproved by Chief of Naval Operations, ADM Ernest King (1878-1956).  Although CAPT Rochefort had died in 1976, Admiral Showers shared the opinion of other surviving members of HYPO that CAPT Rochefort was deserving of the DSM.

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In 1981, Admiral Showers wrote and submitted the paperwork to re-nominate CAPT Rochefort for the DSM.  After some disappointment and initial lack of success, the Secretary of the Navy eventually approved the award in 1986.  Admiral Showers was able to arrange for the DSM to be presented to the Rochefort family by President Reagan.  The presentation ceremony took place on May 30, 1986 at the White House with Admiral Showers in attendance.

Although he never wrote a memoirs of his own, Admiral Showers assisted others in sharing their memories of their service in the war.  He assisted his HYPO shipmate, CAPT Jasper Holmes (1900-1986), in the writing of his 1979 book, Double-Edged Secrets: U.S. Naval Intelligence Operations in the Pacific During World War II.  He helped Edwin Layton (who also retired a Read Admiral) when Admiral Layton wrote his 1985 memoir, And I was There: Pearl Harbor and Midway – Breaking the Secrets.  In 2011, he wrote the foreword to Elliott Carlson’s biography of CAPT Rochefort, Joes Rochefort’s War: The Odyssey of the Code Breaker who Outwitted Yamamoto at Midway.

In 2008, Admiral Showers was inducted into the National Security Agency’s Cryptologic Hall of Honor, an honor previously extended to his shipmates at HYPO, CAPT Rochefort and CAPT Thomas Dyer (1902-1985).

Admiral Showers died on October 19, 2012 at the Virginia Hospital Center in Arlington, Virginia with this two sons and daughter at this side.  He was 93.