William Schull, a 94-year-old U.S. scholar who has spent decades studying the health effects of the U.S. atomic bombings, is a man conflicted who still longs to learn from the tragedies of World War II.

On the one hand, he believes the atomic bombings were an inevitable consequence to end a war Japan started with the U.S. with its surprise attack on Pearl Harbor on Dec. 7, 1941. But war itself, he said, is "the most brutal of human behavior."

As an almost annual affair, Schull visited Japan last month to reunite with lifetime friends in Hiroshima, the first city to be the target of an atomic bomb.