U.S. planning for the invasion and military occupation of Imperial Japan was begun in 1943, two years before the dropping of atom bombs on Hiroshima and Nagasaki. Codenamed Operation Downfall, it called for the invasion to be carried out in two stages. First, the US Sixth Army would storm the southern-most Home Island of Kyushu to provide sites for airfields and anchorages to support a second assault directly at Tokyo, 500 miles north, by the First and Eighth armies.

These facts are well known and have been recounted - with varying degrees of accuracy - in a variety of books and articles published during and since the 50th anniversary of the victory over Japan. One thing that all of these works had in common was an unfortunate tendency to regurgitate material from the same narrow selection of easily obtained planning documents used in each of the other works. An attempt to understand how both the Americans - and the Japanese - planned to conduct the massive land battles subsequent to the initial landings was not dealt with in these books beyond the skeletal US outlines formulated nine months before the opening land battles were to commence, and over a year before the climactic series of battles near Tokyo which would have included not only the First and Eighth armies but the US Tenth Army as well.

On the Japanese side, their plans for Operation Ketsu-Go, the "decisive battle" in the Home Islands, were unexamined below the strategic level and seldom consisted of more than US intelligence estimates of how many Kamikaze aircraft might be available by the time that Kyushu was to be invaded. Hell To Pay: Operation Downfall: the Invasion of Japan, 1945-1947 will examine this subject in detail.