Abstract
This decision was actually matured behind closed doors, not only by the American President but also by his advisers, his ministers and a few scientific experts. Of the many reasons that they invoked during their secret meetings and revealed a posteriori, some of them were undeniably valid but others were more questionable. They were of all kinds : pragmatic, political, military, realistic, ideological, moral, psychological, tactic and diplomatic. Nevertheless, after examining them one by one, it will appear that the military one was the most important in the eyes of Truman, because it reflected the most immediate priority in American foreign policy.
