context: Responsibility for planning the Downfall operation fell on US military leaders: Fleet Admiral Chester Nimitz, Army General Douglas MacArthur and members of the Joint Chiefs of Staff - Fleet Admirals Ernest King and William Leahy, Army Generals George Marshall and Henry Arnold (the latter was led by the US Air Force) [2]. At that time, the development of the atomic bomb was carried out in the strictest confidence under the control of several senior officials; officers planning an invasion of Japan did not know about the existence of the Manhattan project.
question: Who planned Operation Downfall?
answers.text: US military leaders: Fleet Admiral Chester Nimitz, Army General Douglas MacArthur and members of the Joint Chiefs of Staff - Fleet Admirals Ernest King and William Leahy, Army Generals George Marshall and Henry Arnold