Because the U.S. military planners assumed "that operations in this area will be opposed not only by the available organized military forces of the Empire, but also by a fanatically hostile population", high casualties were thought to be inevitable, but nobody knew with certainty how high. Several estimates were made, but varied widely in numbers, assumptions and purposes, which included advocating and opposing the invasion. The estimated casualty figures later became a crucial point in postwar debate over the atomic bombings of Hiroshima and Nagasaki.