Manhattan Project Leaders: Henry L. Stimson

Black and white photo of a middle-aged man with a mustache wearing a suit.
Secretary of War Henry Stimson (pictured in 1929) had direct control of the Manhattan Project.


Quick Facts
Stimson was the Secretary of War for FDR and Truman during World War II and was directly in control of the Manhattan Project.
Place of Birth:
New York, NY
Date of Birth:
September 21, 1867
Place of Death:
West Hills, NY
Date of Death:
October 20, 1950
Place of Burial:
Oyster Bay, NY
Cemetery Name:
Memorial Cemetery of Saint John’s Church

By the time Henry Stimson (1867-1950) joined FDR’s cabinet as Secretary of War in 1940, he had been a US Attorney, Secretary of War under Taft, Governor General of the Philippines, and Secretary of State under Hoover. He had received his BA degree from Yale, his law degree from Harvard, and was a Brigadier General in World War I. When FDR invited him to again take the Secretary’s office, at age 73, it was said he had “energy that men 20 years his junior couldn’t muster.” During World War II he worked with US Army Chief of Staff George C. Marshall to prepare the very unprepared US for war, including organizing housing, training, and equipment for 13 million soldiers and airmen. After the war he insisted on judicial proceedings against Nazi war criminals, leading to the Nuremberg Trials.

Stimson had direct control of the Manhattan Project. He was General Groves’ immediate supervisor, authorized project sites, and made sure that the project had the highest priority for anything needed. He insisted to the Target Committee that Kyoto not be a bombing objective; he respected it for its cultural, religious, and historical importance to the Japanese people, and he and his wife Mabel had spent their honeymoon there. Oppenheimer was surprised and impressed with Stimson’s grasp and concern regarding the future of atomic weapons; he saw that “Stimson was thinking hard and seriously about the implications for mankind of the thing we had created and the wall into the future that we had breached.” After FDR’s death, Stimson gave Truman his first full briefing on the secret Manhattan Project, and he was among the dignitaries who accompanied Groves to witness the Trinity Test. Later, Truman would say of him, “I felt how fortunate the country was to have so able and so wise a man in its service.” In 1948, with McGeorge Bundy, he wrote his memoir, On Active Service in Peace and War.

Manhattan Project National Historical Park

Last updated: August 3, 2023