On This Day. 1945: On Harry Truman's orders, an atomic bomb was dropped on the Japanese city of Hiroshima. The president—who called it “the most terrible bomb in the history of the world"—had been told an invasion of Japan could cost up to one million American casualties /1 
In the weeks before the atomic bomb was even tested, President Truman and his advisors (called the "Interim Committee") carefully studied - agonized, really - over whether to use the bomb, or to invade Japan ("Operation Olympic") in November 1945 /2
In the end, horrendous American casualties on Iwo Jima and Okinawa, and the prospect of even greater U.S. and Japanese bloodshed in an invasion of Japan itself, convinced Truman that the bomb would save more lives than it would take - while shortening the war /3
Did the atomic bombings of Hiroshima and Nagasaki - bombed on Aug. 9, 1945 - save more lives than they took? Here's an excerpt from "Under This Roof," the 2015 book by WWR's Paul Brandus:
