Deak Parsons – The Story of the Atomic Admiral

By Rob Gates

The recent movie Oppenheimer focuses, as expected, on J. Robert Oppenheimer, the eponymous hero of the story and Director of Project Y in Los Alamos. However, it overlooks another important figure – Navy Captain William “Deak” Parsons, an Associate Director of Oppenheimer’s and leader of the Ordnance Division of the Manhattan Project. Parson’s substantial contributions warrant a closer examination, especially his evolution in becoming the “Atomic Admiral.”


William Sterling Parsons was born in Chicago in November 1901 but grew up in Fort Sumner, New Mexico after his father moved the family there in 1909. He was largely homeschooled although he attended the local elementary school for six years starting at age 8. He skipped grades and caught up to and passed his contemporaries. He finished grade school at home after being pulled out of the local school, and started at Santa Rosa High School. He moved from freshman to junior in one year. He was encouraged to take the Naval Academy exam before his senior year, passed it, and became the second alternate. He received the appointment when neither the principal nor first alternate passed the exam.

He reported to the Naval Academy at age 16 for the physical exam. He was viewed as too short and underweight and was rejected. He argued before the examining board that he was younger than the other candidates and, of course smaller, and that he would be the required size when he reached their age. The board bought his argument and gave him a waiver. He became a member of the class of 1922, overlapping with Hyman Rickover’s time at the academy. His family called him Bill but, as was custom at the Naval Academy, he was given a nickname – Deacon, as a play on his last name, which was shortened to Deac or Deak.

Deak Parsons as a Midshipman. (Photo via U.S. Naval Academy)

Early Career

His first assignment after graduation was as a gunnery officer on the USS Idaho (BB-42). After a successful tour, he was sent to the Naval Postgraduate School (NPS) in Annapolis in 1927, where he was a student in the ordnance course and studied under Dr. Charles C. Bramble.1 At the conclusion of the NPS course, students were required to take a field posting, and Parsons came to Dahlgren in early 1930. While there, Dr. L.T.E. Thompson saw promise in him and advised Parsons to become an Engineering Duty Officer so his shore assignments would not be interrupted by periods of sea duty. Parsons saw himself as a line officer and declined the advice. In June 1930, he was assigned to the USS Texas (BB-35).

At the end of that tour, in 1933, he was assigned to the Bureau of Ordnance (BuOrd) as liaison to the Naval Research Laboratory. This proved to be an important assignment, where he was introduced to radar. He became something of an expert in radar and one of its strongest advocates in the Navy, especially for fire control. His advocacy, however, resulted in little as his superiors in the Bureau of Ordnance did not share his enthusiasm.

His next assignments were at sea. He served as the Executive Officer on the USS Aylwin (DD-355) from June 1936 until March 1938. He was then assigned as gunnery officer to improve the gunnery scores of USS Detroit, the flagship of Rear Admiral William R. Sexton, who was serving as Commander of destroyers in the Pacific’s battle fleet. In mid-1939, Parsons was assigned to the Naval Proving Ground in Dahlgren as Experimental Officer. 

Early War Years and the VT Fuze

As Experimental Officer he was responsible for planning and scheduling all testing at Dahlgren. Merle Tuve (of the National Defense Research Committee, NDRC) visited Dahlgren in 1940 to discuss concepts for improved anti-aircraft defense. Parsons knew of Tuve from his radar work and began collaborating with him. He offered Dahlgren’s facilities for testing the early versions of the VT fuze. There was promise but little success in testing at first with 90 percent of the fuzes failing. Finally in January 1942, there were 26 successful tests of a batch of 50 fuzes – exceeding BuOrd’s 50 percent threshold – and Parsons recommended that the fuze go into production. The Navy took over program direction and scheduling but wanted the Office of Scientific Research and Development (OSRD), specifically Vannevar Bush and Merle Tuve, to retain technical direction. Parsons was detailed from Dahlgren to serve as Bush’s deputy overseeing the work of Tuve’s Section T.

Testing of the fuze continued with a successful test in the Chesapeake Bay near Tangier Island in June 1942. The USS Cleveland (CL-55) engaged and destroyed three target drones, reportedly with only three shots. The Cleveland was immediately sent to North Africa and then the Pacific. When an inventory of 5,000 fuzes was available at Mare Island,2 plans were made to send them to the fleet for testing in combat. Parson went onboard the USS Helena (CL-50) and, on January 5, 1943, the ship successfully engaged two Aichi dive bombers and shot down both. He and others spent the next three months training crews in the Pacific on the use of the new weapon.

He returned to Dahlgren at the end of March, hoping to wrap up his fuze work and be assigned sea duty in the war zone. It was not to be.

Project Y – The Manhattan Project at Los Alamos

Vannevar Bush was concerned about Brigadier General Leslie R. Groves’ direction and Army dominance of the Manhattan Project, as well as Groves’ insensitivity to scientists. The Military Policy Committee met and recommended some changes. Groves also wanted an ordnance and fuze expert assigned to the project. No qualified Army officers were available and the opportunity to assign a navy officer, and one who understood military-scientist relationships, presented itself. Bush knew Parsons from his VT fuze work and recommended him to Groves.

Parson subsequently received orders to report to Admiral Ernest King, Commander in Chief, United States Fleet and Chief of Naval Operations, without delay. In a ten-minute meeting, King filled him in on Project Y and then had him meet with General Groves. Groves approved of his appointment and had him meet with J. Robert Oppenheimer, Project Y Director, the next day. Parsons was assigned to King’s staff with the rank of Captain on June 1, 1943 and named Associate Director of Project Y and Head of the Ordnance Division.3

Within a few days the Parsons and Oppenheimer were on the train bound for Los Alamos.4 They spent the time talking before they reached their destination, where they laid out their philosophies and the new organizational structure. Oppenheimer was happy to turn over the responsibilities for ordnance matters to Parsons and to focus on physics. Likewise, Parsons’s strength was in “weaponizing” the bomb and addressing the operational problems associated with its combat delivery.

Parsons had to bring on additional staff and approached people he knew from the VT fuze and radar work. He also went back to the Naval Proving Ground and recruited several people, including Thomas Olmstead, a technician, Norris Bradbury, an expert in exterior ballistics, and Frederick Ashworth, the senior naval aviator at the Proving Ground. Parsons was later criticized for his propensity to hire Navy people.

Parsons also went to Dahlgren for ballistic testing of the gun-type bomb shape. The testing was performed using Parsons’ “sewer pipe” bombs. The test bombs were made by cutting a standard bomb in half and extending the bomb by inserting a length of sewer pipe. The NPG employees and aviators speculated on what they were testing but apparently, no one guessed the right answer.

Parsons’s division was primarily responsible for developing the gun-type/Uranium-235 bomb that was initially called “Thin Man” (after Franklin D. Roosevelt) and, later, “Little Boy.” The division also studied the implosion-type/Plutonium bomb known as “Fat Man” (after Winston Churchill). Plutonium had advantages over Uranium-235, and when it was discovered that it was not suitable for a gun-type bomb, the implosion-type bomb took on greater importance. There was another reorganization in July 1944 and Parsons’s group took on the responsibility of making both bombs combat-deliverable.

From the beginning, Parsons had planned on being the weaponeer for the first combat use of the bomb and expressed that to Groves. When the push to completion started – called Project Alberta – in March 1945, Parsons informed Groves that in accordance with his (Groves) wishes, he was going to be the weaponeer when Little Boy was used. He was officially named the Officer in Charge of the Los Alamos Overseas Technical Group and weaponeer on the first mission.

Frederick Ashworth had been brought in to work with the Army Air Force on the B-29. Parsons planned to fly in a B-29, piloted by Ashworth, over the test at Trinity as a dress rehearsal for the first mission. It did not transpire as he hoped for because he was required to stay 25 miles away from the test site. Nevertheless, he had a great view of the Trinity detonation.

Ashworth led the group that selected Tinian Island as the location of the B-29 base. Once it was constructed, the elements of the bomb, Los Alamos staff, and the 509th Composite Group (under the command of Col. Paul Tibbets) were moved to Tinian. Parsons also went to make final preparations.

Deak Parsons (left), standing next to Col. Paul Tibbets, briefs the 509th Composite Group on Tinian. (Photo via Wikimedia Commons)

After weather delays, the mission was scheduled for August 6. Groves’ direction was that the bomb was to be assembled on the ground before the flight. But Parsons had seen four overloaded B-29s crash on takeoff and was concerned about taking off with a fully armed atomic bomb. Early on August 5, he expressed his concerns to Brigadier General Thomas Farrell, deputy director of the Manhattan Project, reportedly saying, “If that happens tomorrow morning, we could get a nuclear explosion and blow up half the island.” He decided to disregard Groves’ instructions and arm the bomb in flight. He spent the rest of the day (and evening) developing and practicing the process to do just that.

The B-29 took off at 0245 on August 6 and, after it reached cruising altitude, Parsons and Electronics Test Officer, Lieutenant Morris Jeppson entered the bomb bay. Jeppson held the flashlight while Parsons followed the 11-point checklist that he had developed the previous day, and placed the gunpowder-armed fuze behind the Uranium-235 “bullet.” At 0630, Parsons directed Jeppson to return to the bomb bay and replace the green safety plug with a red plug. The bomb was now fully armed, and was successfully dropped at 0915.

That essentially ended Parsons’s role in the Manhattan Project. Ashworth was the weaponeer on the second mission when the Fat Man bomb was dropped on Nagasaki on August 9. The war ended five days later.

Postwar Years

Parsons knew that when he accepted the Manhattan Project assignment that he had given up the opportunity for wartime command at sea. After the war, he concluded that without that command experience, his chances for promotion and his future in the Navy were not good. As it happened, he was promoted to Commodore and Rear Admiral while on Tinian. It also turned out that he was in demand because of his atomic experience and was named technical deputy to the Commander, Operation Crossroads.5 He went on to other positions, including Director of Atomic Defense under the Deputy CNO (Air), and Deputy Director of the Armed Forces Special Weapons Project under General Groves. He also reprised his role as technical deputy to Commander, Operation Sandstone, a series of atomic bomb tests conducted in April 1948. These and other assignments led to his being known as the “Atomic Admiral.”

Detonation of Shot Baker during Operation Crossroads on July 25, 1946.

In 1951, he finally got his command at sea when he was named Commander, Cruiser Division Six in the Atlantic Ocean and Mediterranean Sea. In March 1952, he became Deputy Chief, Bureau of Ordnance and his future looked bright, He used his influence to promote research and establish Navy laboratories and, because of his expertise, was involved in many technical initiatives. He was busy to the point of exhaustion.

When he went to Los Alamos in 1943, he worked closely with Oppenheimer. They lived in adjacent houses on “Bathtub Row” (so called because they were the largest houses in Los Alamos and the only ones on the mesa with bathtubs) and their families became close. They stayed in touch after the war and occasionally vacationed together.

Rear Admiral Deak Parsons. (Photo via

When Parsons learned that President Eisenhower had decided that a “blank wall be placed between Dr. Oppenheimer and secret data,” effectively negating Oppenheimer’s Q-level security clearance, according to Parson’s wife, he became “visibly upset” and began to suffer chest pains. He concluded that it was not a heart attack but, when he was no better the next morning, his wife insisted that he go to the Bethesda Naval Hospital. While being prepared for an electrocardiogram, the Atomic Admiral died at the age of 52 on December 5, 1953.

Although Deak Parsons died young, his contributions to the Navy were significant and his legacy is intact. His early Navy career was much like many other junior officers of the time, but even then, his expertise in ordnance and gunnery were apparent. His legacy came later in his career and is mostly seen in his technical contributions, beginning at the Naval Proving Ground. His partnership with Dr. L.T.E. Thompson had a great impact on the Proving Ground and the Navy. Their vision was of a naval laboratory where scientists and officers would work closely together on creative research that was key to the Navy’s future. This vision would take root and set the pattern for Navy laboratories that has persisted to the present. His contributions to the Variable Time fuze and Project Y show the successful application of that principle to some of the most important projects of World War II. After the war, Parsons became the Navy’s leading authority on nuclear issues and an early advocate of nuclear power for ships and nuclear strike capability for aircraft carriers. In short, he helped lead the Navy into the nuclear age. He was on track to become the Chief of the Bureau of Ordnance when he died. Undoubtedly, many more accomplishments would have followed.

Robert V. (Rob) Gates, a retired Navy Senior Executive, served as the Technical Director at the Naval Surface Warfare Center (NSWC), Indian Head Division, and in many technical and executive positions at NSWC, Dahlgren Division, including head of the Strategic and Strike Systems Department. He holds a B.S. in Physics from the Virginia Military Institute, a Masters in Engineering Science from Penn State, and a Masters and PhD in Public Administration from Virginia Tech. He is a graduate of the U.S. Naval War College.  Dr. Gates is the Vice President of the board of the Dahlgren Heritage Foundation.


Baldwin, Ralph B. The Deadly Fuze: Secret Weapon of World War II, Presidio Press, 1980.

Bird, Kai and Martin J. Sherwin, American Prometheus: The Triumph and Tragedy of J, Robert Oppenheimer, Alfred A. Knopf, 2005.

Christman, Albert B. Target Hiroshima: Deke Parsons and the Creation of the Atomic Bomb. Annapolis, Naval Institute Press, 1998.

Christman, Al, “Deak Parsons: Officer-Scientist.” U.S. Naval Institute Proceedings, 56-61, January 1992.

Christman, Al, “A New Kind of Officer.” U.S. Naval Institute Proceedings, 79-80, May 1998.

Furer, Julius Augustus, Administration of the Navy Department in World War II, Department of the Navy, 1959.

Gates, Robert V, “Dahlgren’s Secret: It’s People,” Northern Neck of Virginia Historical Magazine, 9458-9470, December 2022.

McCollum, Kenneth G., Ed, Dahlgren, NSWC, 1977.

Rife, James P. and Rodney P. Carlisle, The Sound of Freedom: Naval Weapons Technology at Dahlgren, Virginia 1918-2006, NSWCDD, 2007.

Rowland, Buford and William B. Boyd, U.S. Navy Bureau of Ordnance in World War II, Bureau of Ordnance, Department of the Navy, 1953.

Stern, Philip M. and Harold P. Green, The Oppenheimer Case: Security on Trial, Harper & Row, 1969.


1. Interestingly, Bramble also has a connection to Dahlgren. He occasionally visited Dahlgren, while teaching at the NPS, to stay current in ordnance developments (starting in 1924). He came to Dahlgren in 1942 when ordnance work was moved out of Washington and stayed until 1946, when he went back to the NPS. He returned to Dahlgren in 1947 and stayed until the end of 1954. He was Dahlgren’s first Director of Research beginning in 1951. He was succeeded by Dr. Russell Lyddane, the first to be called Technical Director.

2. Ten per cent of each batch was sent to Dahlgren for testing.

3. He continued to be listed as a member of King’s staff since it provided “cover” and kept his actual assignment secret.

4. Groves prohibited senior project leaders and scientists from flying. He changed his policy in the spring of 1945.

5. Operation Crossroads was a pair of atomic bomb tests at Bikini Atoll in mid-1946.

Featured Image: The “Baker Day” atomic bomb test, Bikini Atoll, July 25, 1946.

4 thoughts on “Deak Parsons – The Story of the Atomic Admiral”

    1. Very enjoyable article. I attended many courses at the Deak Parsons Center during my naval career. It was a great place to learn current nuclear related subjects and also see nuclear weapons development and history in painting and photographs in the halls and classrooms.

  1. Sadly there are some errors. Captain Parsons was promoted to Commodore the day after the bombing of Nagasaki while he was still on Tinian. He was promoted to Rear Admiral in January 1946. Had he not had the premature heart attack, he probably would have been eventually promoted to Admiral.

    Captain Parsons also witnessed the Trinity Test standing behind the pilot of a B-29 that flew about 40 miles from the test site. Commander Ashworth probably did not witness the Trinity Test and he would never have flown a B-29. He was not qualified to pilot a B-29.

    My source is the excellent book Target Hiroshima by Al Christman and actually Wikipedia for the dates of promotion which are not that clear in the book.

  2. My father was Admiral Parsons Flag Lt. and personal aide aboard the USS Macon as Commander Cruiser Divison Six. Since my fathers passing I have been struggling to determine how best to identify and distribute the many photos I have of Admiral Parsons and many guests and dignitaries he received while aboard the USS Macon in the Med. Any help or advise would be appreciated.

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