On June 29, 1946, the Manhattan Engineer District published their report, The Atomic Bombings of Hiroshima and Nagasaki, describing the effects of the atomic bombs. The report was compiled under the direction of Major General Leslie Groves, who instructed Brigadier General Thomas Farrell to organize a special Manhattan Project Atomic Bomb Investigating Group. Their mission was to secure scientific, technical, and medical intelligence about the atomic bomb effects from Hiroshima and Nagasaki as soon as possible after the cessation of hostilities.
Farrell arrived in Hiroshima on September 8, 1946, equipped with portable geiger counters. Along with Brigadier General James Newman, Dr. Masao Tsuzuki (member of the Atomic Bomb Casualty Commission also acting as translator), and Colonel Stafford Warren, the head of the Manhattan District’s Medical Section. They remained in Hiroshima until September 14, then surveyed Nagasaki from September 19 through October 8.
The dropping of the two atomic bombs raised many military and medical questions that would eventually lead to more nuclear tests, specifically Operation Crossroads.
Concurrently with the Manhattan District’s survey teams, the United States Strategic Bombing Survey also conducted research on the effects of the atomic bombs on Hiroshima and Nagasaki. This report (The United States Strategic Bombing Survey: The Effects of Atomic Bombs on Hiroshima and Nagasaki), published on June 30, 1946, incorporated much of what was included in the Manhattan District’s report, but more from a “lessons learned” perspective as well as future implications for use of the atomic bomb on others or on the United States. The report’s somewhat convoluted conclusion regarding the use of the atomic bombs in influencing Japan’s surrender is that it created the excuse for them to accept the Potsdam terms while saving “face” — no army without the weapon could possibly resist an enemy who had it.