To gain a sense of the historical context for the atomic bombing of Hiroshima and Nagasaki we recommend viewing and reading:
The Decision To Drop The Bomb (1965)
The Last Empire: Intervention and Nuclear War
Empire and the Bomb Chapter 2: First Nuclear Terrorism – Hiroshima and Nagasaki by Joseph Gerson
Gar Alperovitz: 60 Years Later, Historians Are Still Arguing
The Bomb in American Memory – Harvard University Press