THE END OF THE COLD WAR? By Thomas W. Simons Jr. St. Martin's. 188 pp. $16.95

THIS MODEST volume is hardly the first, nor will it be the last, to bear its timely title. Historians should not object, though, because they are going to need all the help they can get in explaining why almost half a century of confrontation between the United States and the Soviet Union has now ended with neither bang nor whimper, but with the other side simply acknowledging: "You've been right all along."

It was Mikhail Gorbachev who in effect made that striking admission, and even if he should be overthrown tomorrow history will surely award him the lion's share of credit for having brought the Cold War to an end. But Ronald Reagan played a role in these events as well; historians are much less certain than in the case of Gorbachev, however, about just what that role was. Did the Reagan administration actively seek to end the Cold War, or was it simply responding passively -- and with as much astonishment as everyone else -- to the Gorbachev revolution?

Not surprisingly, former Reagan administration officials tend to favor the first over the second line of argument, and Thomas W. Simons Jr., currently the United States ambassador to Poland, is no exception to this pattern. Simons served as deputy assistant secretary of state for European and Canadian affairs during the Reagan years; his special responsibilities were the Soviet Union, Eastern Europe and Yugoslavia. But Simons was trained as an historian, and this book -- prepared from a set of lectures he delivered while diplomat-in-residence at Brown University in 1989 -- is intended to make the point that the Reagan administration was in fact seeking to end the Cold War long before Gorbachev came to power.

Simple chronology lends a certain plausibility to this argument: Reagan had quite openly begun to shift, by the middle of 1983, to a more conciliatory Soviet policy than the one he had followed during his first two years in office. The administration's measured reaction to the Korean airliner incident in September of that year, its growing interest in arms control and its repeated offers to undertake negotiations with a succession of infirm and unresponsive Soviet leaders all suggest that the president and his advisers were already moving away from their their hard line at a time when few of them had even heard of Gorbachev.

The reasons for this shift, though, are less clear. Was the administration improvising in response to the opposition its belligerent rhetoric had sparked, or had it planned this combination of initial toughness with subsequent flexibility all along? Simons argues strongly for planning, and he even advances the intriguing suggestion that Jimmy Carter, had he been reelected in 1980, would have followed much the same course. Both presidents, Simons maintains, were responding to the American public's delayed realization that the architects of detente in the 1970s had been (to use a currently fashionable term) "declinists": Detente had assumed diminishing American influence in the world without attempting to counter that trend, and the public was no longer prepared to put up with that. It was Carter who reversed the decline in defense spending in 1978, and Reagan -- albeit more dramatically -- followed suit. The new strategy was in fact an old idea: negotiation from strength. BY THIS LOGIC, then, the Reagan administration's hard line during its first term was necessary to regain the initiative from the Russians, to rebuild self-confidence at home and to solidify the NATO alliance. All of that had been accomplished by 1983, Simons argues; meanwhile the administration had been careful to combine this approach with a series of highly publicized and easily grasped negotiating positions -- the "zero option" on intermediate-range nuclear forces, a 50 percent reduction in strategic forces, and President Reagan's own distinctive idea, articulated in his proposal for the Strategic Defense Initiative, of ultimately rendering nuclear weapons obsolete -- which put both its domestic critics and the Russians on the defensive while at the same time preparing the way for serious negotiations. Gorbachev may have actually ended the Cold War, therefore, but Reagan -- and even Carter -- had been working toward

hat end as well.

Simons cites no sources for this interpretation other than his own impressions from what he admits was a limited angle of vision: "Even as an insider I was not privy to many facts that may in retrospect seem more important than those presented here." He is self-effacing to a fault in describing his own participation in these events, and even the administration's top policymakers remain shadowy figures in his exceedingly bland and discreet account of what took place. This is, by no stretch of the imagination, a "kiss-and-tell" memoir.

But Simons does remind us of several points that are all too easy, now, to forget: that there were continuities as well as differences in the Carter and Reagan foreign policies; that Reagan the cold warrior never ruled out the possibility of becoming a peacemaker; that Soviet-American relations were slowly improving before Gorbachev took power; and that we should probably pay more attention than we do to the public pronouncements of politicians, for in the case of Ronald Reagan what he said -- at least as far as relations with the Russians were concerned -- was a pretty good guide to what he actually did.

Simon's book is a first draft of history. Subsequent research will show it to be wrong in places, perhaps even wrong altogether. But it will be a while before that kind of research can take place, and in the meantime this small book, skeletal though it is, is worth taking seriously as a starting point in explaining how the United States under Ronald Reagan came to make its own contribution to the praiseworthy task of ending the Cold War. John Lewis Gaddis is Distinguished Professor of History and director of the Contemporary History Institute at Ohio University. His most recent book is a new edition of "Russia, the Soviet Union, and the United States: An Interpretive History."