Was Hiroshima necessary?

THE decision to drop the atomic bomb on Hiroshima and one other city was the most fateful in recorded history. It not only obliterated two large cities and some 200,000 lives and brought to an end the war with Japan; it irretrievably changed the nature of warfare. And by launching a nuclear arms race, it profoundly altered the world economy, the character of international relations, and the goals of scientific research, and it threatened the survival of mankind -- of all living creatures and of nature. Was it necessary to drop the bomb? Was it wise?

The ``official'' answer is familiar, even hackneyed. The alternative, we are assured, was an invasion that would have cost half a million to a million American lives and doubtless even more Japanese. Thus, even quantitatively, the bombs were more ``merciful'' than the alternative of an invasion.

This argument has little or no validity. Granted, an invasion even with Soviet aid (which is never mentioned in the calculations) might have cost a million lives. But why grant an invasion?

Given the practical situation in August 1945, an invasion would have been madness. Japan was irretrievably defeated: Even its most extreme military leaders recognized that and were bent on preserving ``honor,'' not on defeating the enemy. Its Navy had been shattered; its Air Force was reduced to a few thousand kamikaze planes, which might have inflicted severe damage on an invading force, but had little success against American naval ships; its cities were all but defenseless and the America n Air Force could have wiped out every major city almost at will, as it all but wiped out Tokyo, by traditional bombing. Japan's merchant ships had been reduced from over 10 million to less than 2 million tons, and American submarines were taking a daily toll of what was left. With VE Day in Europe, Britain had already taken the offensive in the Far East, ousting the Japanese from Rangoon and Burma, and Russia stood poised in Korea to take part in an invasion of the home islands.

All the United States needed to do to end the war was to fight off the ever diminishing supply of submarines and kamikaze planes and await the inevitable end.

Did we decide to drop the bombs to hasten that end? As Kai Erikson has pointed out, there was no formal decision -- that ``mature consideration'' which the Roosevelt-Churchill memorandum called for. The decision, as Robert Oppenheimer later confessed, was ``implicit in the project.''

Was the fateful step taken in order to forestall a Soviet invasion of Japan? Was it taken to dramatize to the world that none now could ``bridle Behemoth, or curb Leviathan''?

When Niels Bohr, the dean of nuclear physicists, visited Winston Churchill to warn him of the incalculable dangers of the nuclear bomb, Churchill's response was to warn Franklin Roosevelt that he should have Bohr ``watched.'' When Leo Szilard -- another of the Nobel Prize physicists responsible for the bomb -- and a large number of the Manhattan Project physicists tried to reach Harry Truman with similar warnings, their message was pocketed by Gen. Leslie Groves.

Those who made the ultimate decision never sought formally to rationalize it. It was Churchill who wrote the epitaph to what may be the final act in the drama of history:

``Mankind is now placed in a situation both measureless and laden with doom. Now safety will be the sturdy child of terror, and survival the twin brother of annihilation.''

Historian Henry Steele Commager is Simpson Lecturer at Amherst College.