Barack Obama will be the first U.S. president to visit Hiroshima, a prospect that has set off arguments about whether he should apologize for our use of nuclear bombs to end World War II. The White House says he will not. While the case that he should is strong, the case that he shouldn't is stronger.

Most Americans, from 1945 to the present, have believed that President Harry Truman was justified in bombing Japan. Most supporters of that decision say the bombs saved lives by breaking Japan's will to continue fighting. The alternative, they add, was a ground invasion that would have caused much more blood, Allied and Japanese, to be shed.

But there are others who dispute the claim that the bombs were necessary to bring about Japan's unconditional surrender. An official U.S. government report in 1946 concluded that "it seems clear that, even without the atomic bombing attacks, air supremacy over Japan could have exerted sufficient pressure to bring about unconditional surrender and obviate the need for invasion."