FDR writes to Manhattan Project physicist Dr. Robert Oppenheimer - Jun 29, 1943 - HISTORY.com

On this day in 1943, President Franklin D. Roosevelt writes a letter marked “secret” to leading Manhattan Project physicist J. Robert Oppenheimer. In the letter, Roosevelt sought to smooth over the growing antagonism between Oppenheimer and General Leslie Groves, the military leader in charge of the project.

Roosevelt began by congratulating Oppenheimer (or “Oppie” as he was known to colleagues and friends) on the progress of a “highly important and secret program of research, development and manufacture with which you are familiar.” No mention was made, of course, of the phrase “Manhattan Project” or “atomic bomb.” Roosevelt conveyed a sense of urgency in solving “the problem” and bringing the project to fruition. He stressed the project’s bearing on national security.

Roosevelt’s letter acknowledged Oppenheimer as the leader of an elite group of scientists operating under strict security and under “very special conditions.” He had received reports that the brain trust of scientists tapped to deliver an atomic weapon were starting to snap under the pressure of trying to meet what they saw as an impossible deadline. Oppenheimer and Groves frequently clashed over the scientists living and working conditions. The small isolated community resented living under heavy guard in the desert of New Mexico. Many of the experts had doubts the bomb could even be built at all and questioned the wisdom of working with such dangerous material.

Roosevelt appealed to Oppenheimer to convince the group of the necessity of the restrictions and asked him to convey his appreciation for their hard work and personal sacrifice. Roosevelt expressed his faith that “whatever the enemy may be planning, American science will be equal to the challenge.” The letter reflected Roosevelt’s natural ability to rally morale–whether it was subduing revolt among physicists working on a crucial new weapon or reassuring American mothers of the need for food rationing in a time of war.

Two years later, at a test site near Alamogordo, New Mexico, the first atomic bomb was successfully detonated. Roosevelt would not live to decide whether or not to use the new and powerful weapon in World War II. He died on April 12, 1945, leaving the decision to his successor, Harry S. Truman. Truman authorized the use of the world’s first atomic weapons against Japan on August 6 and 9, 1945.