The question of whether it was wise and necessary for the United States to use nuclear weapons against an enemy in wartime has always seemed to me cut and dried. Of course it was. The interesting question over the years has been whether, as some believe, the United States dropped the bombs on Hiroshima and Nagasaki to intimidate an ally in peacetime. Specifically, did we mean to initiate "atomic diplomacy" and make the Soviet Union bow to American postwar territorial and political designs?

Did we take the leap into the atomic age, in the process killing great numbers of Japanese, primarily to impress Joseph Stalin and to advance otherwise unworthy American interests? On both sides, those who have debated this question have understood what a terrible and indefensible thing it would have been. Among other results, it would have put upon the United States the principal blame for destroying the wartime anti-Hitler alliance and starting the Cold War.

For exactly this reason, the Soviets, playing on the still-considerable American guilt and confusion about the bomb, continue to insist that the United States in 1945 did indeed practice "atomic diplomacy." Just the other day at Geneva, for instance, Georgi Arbatov, a familiar spokesman, and Andrei Gromyko's son Anatoly renewed the charge that the bombs had been dropped to impress the Kremlin.

I first came upon the charge in 1965 upon publication of Gar Alperovitz's "Atomic Diplomacy: Hiroshima and Potsdam," a provocative revision of the generally benign and then generally accepted view of the decision to use the bomb. Alperovitz argued that the bomb had determined much of Truman's ostensible shift to a tough anti-Soviet policy in Europe. I recall writing him an intemperate letter; perhaps, in retrospect, given the mischief of the charge, not intemperate enough.

In any event, in due time more scholarly responses were prepared using materials not available when Alperovitz was writing. This makes it possible, I believe, to support the simple, square, old-fashioned view that Truman dropped the bomb to win the war, and to support it not simply on the basis of a distaste for the revisionist blame-America historians of the 1960s and 1970s but on the basis of the historical record.

There was, to be sure, a great flush of excitement when news of an impending bomb first spread. Daniel Yergin recalls Secretary of State James Byrnes said (all of this privately), "The New Mexico situation (the first test) had given us great power." Winston Churchill was elated that "We now had something in our hands which would redress the balance with the Russians." Secretary of War Henry Stimson, detecting "a great change . . . in my own psychology," thought we had the "master card" to a postwar settlement. "Most of the Americans who knew about the bomb thought it could be put to work in diplomacy," writes Yergin in "Shattered Peace," "but did not know how."

They never learned. Stimson brimmed with fuzzy thoughts about vast newly conferred American influence in Asia as well as Europe. But the specific application he came up with was not to wield the bomb as a stick but to offer it to the Russians as a carrot; the Russians wouldn't have it. Averell Harriman, then our Moscow ambassador, says that at the crucial pre-Hiroshima Potsdam summit (40 years ago this week), the bomb "never entered the discussions." Flying home from Potsdam, Charles Bohlen and Llewellyn Thompson, our top Soviet hands, pondered the bomb's possible influence on Soviet-American relations and found no way it could be brought to bear.

Adam Ulam, the Harvard scholar, adds in "Dangerous Relations" that "no one has presented a single piece of evidence showing that the U.S. ever employed its then-monopoly of nuclear weapons to wrest concessions from the U.S.S.R. And even more to the point, no one has explained what it was that the American atomic blackmail allegedly prevented the Kremlin from doing." Or as a detective story reader might put it: no gun, no corpse.

Ulam offered a footnote to his book in a conversation this week. The Soviets never brought up the charge that the United States had attempted to use its nuclear monopoly for coercive political purposes, he told me, until the American revisionist historians started writing about it. That is to say, the whole notion of "atomic diplomacy" arose in the first instance not from real Soviet apprehension and not even from Soviet propaganda but from the workings of our own free society.