The anniversaries of the atomic bombings of Hiroshima and Nagasaki present an opportunity to demolish a cornerstone myth of American history — that those twin acts of mass civilian slaughter were necessary to bring about Japan's surrender, and spare a half-million US soldiers who'd have otherwise died in a military conquest of the empire's home islands.

Those who attack this mythology are often reflexively dismissed as unpatriotic, ill-informed or both. However, the most compelling witnesses against the conventional wisdom were patriots with a unique grasp on the state of affairs in August 1945 — America's senior military leaders of World War II.

Let's first hear what they had to say, and then examine key facts that led them to their little-publicized convictions:

General Dwight Eisenhower on learning of the planned bombings: "I had been conscious of a feeling of depression and voiced to [Secretary of War Stimson] my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives. It was my belief that Japan was, at that very moment, seeking some way to surrender with a minimum loss of 'face'."

Admiral William Leahy, Truman's Chief of Staff: "The use of this barbarous weapon…was of no material assistance in our war against Japan. The Japanese were already defeated and ready to surrender because of the effective sea blockade and the successful bombing with conventional weapons."