Casualty Estimates for the Invasion of Japan: What did the Truman Cabinet Know?

Abstract

There has been much controversy surrounding the casualty estimates for the invasion of Japan given by the Truman Cabinet and other key leaders involved with the Manhattan Project. Much of this is because there is such a wide range of estimates; starting with those under 100,000 to more staggering figures in the millions. Supporters of different numbers are often grouped according to their ideological or political lines of reasoning. While revisionist historians and anti-nuclear advocates tend to agree on smaller numbers, military historians and war veterans generally support higher numbers, especially those found in orthodox estimates. Fifty years after the atomic bombs these debates reached a boiling point as the Smithsonian Museum prepared for exhibition of the Enola Gay. Many scholars have contributed to this debate by coming up with independent estimates using various historiographical and mathematical techniques. In regards to casualty estimates for the invasion of Japan, John Ray Skates, a former professor at the U.S. Army Center of Military History in Washington D.C. considers it "the most hotly contested subject in the debate over the atomic bomb." The purpose of this essay is to explain why the casualty estimates for Japan have become such an important fixture in understanding the end of the Pacific War, specifically the climactic bombings of Hiroshima and Nagasaki. First, a brief history of how the bombs came to be questioned after the first one was dropped and the subsequent justifications that developed. Secondly, in order to more fully appreciate the complexity of the subject a brief discussion of casualty estimate definitions, challenges, and techniques will be made. This will be concluded by a review of pre-surrender and post-surrender casualty estimates and the debates that surround them. There are many casualty estimates that can be discussed, including those found in various military documents, independent assessments, and Japanese estimates. The focus of this essay will be on the high-level estimates given by members in the Truman cabinet, especially those by President Truman and Secretary Stimson. To a lesser extent, casualty estimates given by Manhattan Project leaders will be discussed. The scientific leaders of the Manhattan Project were focused on research, development, deployment, and targeting of the atomic bombs. Making casualty estimates for the invasion of Japan was neither their responsibility nor their focus, and rarely did they attend meetings where such topics were discussed. High-level discussions of this sort involved the Secretary of War, the Joint Chiefs of Staff, and only a few other select members of Truman's cabinet. Only after the atomic bombs were dropped and the public pressured justification did it behoove some Manhattan Project leaders to become involved in casualty estimate debates for the invasion of Japan. Prior to the atomic bombings of Hiroshima and Nagasaki in 1945, the Truman cabinet and leaders of the Manhattan Project were busily preparing themselves for the American public. On August 6, 1945, shortly after the first bomb was dropped on Hiroshima, President Truman and Secretary of War Stimson released official statements to the public. Both releases were largely concerned with announcing the world's first use of the atomic bomb and explaining the history of research and development of the new technology. In a thorough reading of their statements, it is clear that President Truman and Secretary Stimson were not overly concerned about explaining or justifying themselves in regards to the use of the bombs. As will be shown, this is not surprising given the state of affairs at that time.