William R . Purnell Rear Admiral William Reynolds Purnell ( 6 September 1886 – 3 March 1955 ) was an officer in the United States Navy who served in World War I and World War II . A 1908 graduate of the United States Naval Academy , he captained destroyers during World War I . He was awarded the Navy Cross for his role in protecting convoys against German submarines as commander of the . He was promoted to rear admiral in November 1941 . During World War II , he was Chief of Staff of the ill - fated Asiatic Fleet at the start of the Pacific War . He later served as Assistant Chief of Naval Operations for Materiel . He was the Navy representative on the Joint Committee on New Weapons and Equipment , and , from September 1942 , the Navy representative on the Military Policy Committee , the three - man committee that oversaw the Manhattan Project . Purnell helped coordinate the activities of the Manhattan Project with those of the Navy . In 1945 , he travelled to Tinian as the representative of the Military Policy Committee , and coordinated preparations for the atomic bombing of Hiroshima and Nagasaki with senior Army and Navy commanders in the Pacific . He retired from the Navy in 1946 and died in 1955 . Early life . William Reynolds Purnell was born in Bowling Green , Missouri , on 6 September 1886 . In 1908 , he graduated from the United States Naval Academy at Annapolis . He was commissioned as an ensign in 1910 . During World War I , he commanded the destroyer s , , , and . For his services , he was awarded the Navy Cross . His citation read : In January 1917 , while he was serving on the " Rowan " , he married Ada Dodge Curtiss , the daughter of Walter Phelps Dodge and the ex - wife of Gerald S . Curtiss . They had one son , William Reynolds Purnell , Jr . After the war , he commanded the tanker from 1934 to 1936 . Alternating duty afloat with service ashore , he then became secretary to the General Board . He commanded the cruiser from January to December 1939 . World War II . Purnell became Chief of Staff of Admiral Thomas C . Hart ' s Asiatic Fleet . Purnell represented the United States at a planning conference in Singapore in April 1941 at which American , British , Dutch , Australian , and New Zealand commanders attempted to coordinate their plans for an increasingly likely war with Japan . He was promoted to rear admiral in November 1941 . On 7 December , Purnell played golf with Hart . War broke out the next morning . The Japanese advanced quickly and the Asiatic Fleet moved from the Philippines to Java in January . As the Japanese closed in on Java , Purnell flew to Broome on 25 February . In Australia , Purnell became Chief of Staff to Vice Admiral William A . Glassford , the Commander , US Naval Forces , Southwest Pacific . When Glassford departed in May 1942 , Purnell took his place . He too left Australia in June 1942 , for duty in Washington , DC , in the Office of the Commander in Chief , United States Fleet , Admiral Ernest J . King . For his services , he was awarded the Navy Distinguished Service Medal . His citation read : Purnell became Deputy Chief of Naval Operations for Materiel . He was also the Navy representative on the Joint Committee on New Weapons and Equipment , and , from September 1942 , the Navy representative on the Military Policy Committee , the three - man committee that oversaw the Manhattan Project . Purnell helped coordinate the activities of the Manhattan Project with those of the Navy , particularly the navy ' s thermal diffusion research , and he helped provide scientists and technicians from the Navy for the project . In February 1945 , Purnell arranged for Commander Frederick Ashworth to go to Guam to brief Fleet Admiral Chester Nimitz on the project . He provided Ashworth with a letter from King stressing the project ' s importance and the need for secrecy . Ashworth selected a base site for the Manhattan Project ' s operations . He inspected facilities on Guam and Tinian , and chose the latter . Tinian ' s harbor suffered from congestion due to extensive base development work , and ships sometimes took months to unload . The director of the Manhattan Project , Major General Leslie R . Groves , Jr . , went to Purnell , who arranged for an order from King to Nimitz stating that all shipments related to the Manhattan Project and the 509th Composite Group had to be unloaded immediately on arrival , regardless of the consequent disruption to the port ' s operations . Problems like this underlined the value of having high - ranking officers on hand to deal with local commanders to make decisions on the spot if necessary . In drawing up an organization for command of the Manhattan Project ' s operations , Groves and Purnell agreed that Purnell should to be present on Tinian as both the representative of the Military Policy Committee and the personal representative of Admiral King . He was joined by Brigadier General Thomas F . Farrell , the Manhattan Project ' s Deputy for Operations , and the two shared responsibility for coordinating the Manhattan Project ' s activities with the senior Army and Navy commanders in the Pacific . Along with Captain William S . Parsons , the director of Project Alberta , they formed what became informally known as the " Tinian Joint Chiefs " . Purnell was the first proponent of the idea that two atomic attacks , one following quickly after the other , would be required to end the war . This was something that Groves and Purnell discussed a number of times . " I knew that with him and Farrell on the ground at Tinian , " Groves wrote . " There would be no unnecessary delay in exploiting our success " after the bombing of Hiroshima . The main difficulty with the second mission , then scheduled for 11 August , was the weather , which was predicted to be good until 9 August but bad for at least five days starting on 10 August . Parsons agreed to work the assembly team around the clock to get the Fat Man bomb ready by the evening of 8 August . Before Major Charles Sweeney took off on the mission , Purnell took him aside and asked him if he knew how much the bomb cost . Sweeney did not know ; Purnell told him it was about $ 2 billion . He then asked if Sweeney knew how much his aircraft was worth . This Sweeney did know ; over half a million dollars . Purnell then told him : " I ' d suggest you keep those relative values in mind for this mission . " Later life . After the war , Purnell served as a member of the Army - Navy Evaluation Board during Operation Crossroads . He retired from the Navy in October 1946 , and moved to Palo Alto , California , where he died on 5 March 1955 . He was buried in Golden Gate National Cemetery . He was survived by his wife , Ada Dodge Purnell , and his son , William R . Purnell , Jr .