Whatever happened to America's detente with the Soviet Union -- whatever that was?

It seems barely yesterday that America's leaders were promising "a generation of peace," as Richard M. Nixon like to put it. The year 1972 -- a great vintage for the soothing elixir of detente -- could be marked by future historians as "the year when America helped to lead the world out of the lowlands of constant war, and onto the high plateau of lasting peace," Nixon said that June in an address to Congress.

Now the conventional wisdom goes in the opposite direction. Now the sloganeers speak of going "back to square one," or "back to the Cold War." But square one has disappeared with the passage of time; the Cold War -- an era of overwhelming American superiority, as well as tense Soviet-American relations -- cannot be recreated.

Perhaps this detnete -- a French word for what was supposed to be an American policy -- was never clearly understood. Henry A. Kissinger tried to define it originally, but he had a complicated idea -- perhaps it was a European idea. It never really caught on here. Kissinger argued that the Russians were still the bad guys, but that we could cooperate with them anyway, at least in some areas. This may have made perfectly good sense in Kissinger's terms, but it baffled many Americans. In America, the bad guys usually wear black.

Kissinger said the United States could wrap the Soviet Union in a web of new international agreements and understandings. He offered himself as the spider who would spin this web.But American foreign policy is inevitably the product of many spiders, and Kissinger could never control them all.

Almost at once other spiders began to impose their terms on Kissinger's detents. Early on, for example, proponents of freer emigration of Jews from the Soviet Union effectively scuttled the Soviet-American trade agreement by imposing conditions on the granting of trade benefits to the Soviets. This was American democracy in action, but it utterly confounded Kissinger's plans.

The Soviet never demonstrated the kind of moderation that detente had seemed to promise. Even in October 1973 -- when the elixir of detente was, theoretically at least strongest -- the Russians saw the Yom Kippur war coming but did nothing to stop it or warm the United States. In the mid-1970s, using Cuban surrogates, the Soviets began a series of unprecedented African adventures. Repeated crackdowns on Jews and other dissidents in the Soviet Union also defied many Americans' expectations for the new superpower relationship.

As circumstances peeled away one after another of the hopes for detente, only one important area was left: strategic arms control. To the very end, both sides talked of other benefits, real or anticipated, but in the last YEARS ONLY THE STRATEGIC ARMS LIMITATION TREATY (SALT) had really been at stake. This turned out to be too thin a recd to restrain the instinctive animosities and amibitons that still divide two vastly different societies.

The Soviet invasion of Afghanistan was an announcement that the detente of the '70s had run its course -- the Russians were no longer interested in being restrained.

The rosy detente that President Nixon foresaw in 1972 never really took hold. Perhaps it never had a chance. Neither side was prepared to sacrifice its traditional interests or instincts for the sake of their mutual relationship. The Early PHASE

There were attempts to improve East-West relations through the 1950s and 1960s, but a series of events in 1969 created the conditions for a new departure in international affairs. That was the year Nixon came to office with talk of a new era of negotiations. NATO leaders gathered in Washington that spring and agreed that it was time to move toward East-West detente. In September Willy Brandt's Social Democratic Party won the West German elections, a mandate for Brandt to pursue vigorously his "Ostpolitik," or eastern policy, toward European detente.

The early phase of this new detente was primarily a European affair. The United States played a secondary, and initially a skeptical, role. Brandt's first initiatives seemed too much too soon to the Nixon administration, but they led to the resolution of the German problem" that had bedeviled East and West since 1945.

Brandt resolved it by accepting this status quo imposed by Soviet arms in the war. In return, Brandt said, the Soviets would have to allow relations between West and East Germany and the rest of Eastern Europe to relax. And this they did.

The year 1969 was crucial in another arena too. China and the Soviet Union engaged in open hostilities in 1969 along the Ussuri River. At about the same time, the Soviets hinted they might be considering a preemptive strike against China's infant atomic weapons program. These events, coupled with the previous year's vague but threatening "Brezhnev Doctrine" suggesting that all communist countries were subject to Soviet intervention (enunciated by Leonid I. Brezhnev after the Soviet invasion of Czechoslovakia), must have alarmed Peking.

The specter of China runs through all of this tale. It has been a continuing prod to the Soviet Union to improve conditions on the more stable western frontiers of its empire -- in other words, an impetus to the 1960s detente. Nixon and Kissinger expoloited this perceived threat with their unexpected opening to China in 1971, which itself exploited Chinese fears of the Soviets.

Until 1971 the American interest in improved East-West relations had limited and practical purposes, most of them related to the threat of thermonuclear war. The 1963 Test Ban Treaty and the 1969 decision to begin serious strategic arms limitation talks were the principal manifestations of that interest.

In 1971 Nixon and Kissinger moved toward a larger ambition -- "to maintain America's place in the world at a reduced price," as Prof. Robert Tucker of Johns Hopkins University put it in an interview last week.

This was the essence of Kissinger's notion that the Russians could be ensnared in a new, diplomatically negotiated web of East-West commitments that would make them more reasonable. The Soviet View

Soviet motives for moving toward "a relaxation of international tensions" -- the Soviet term for detente -- have always been a matter for debate. But some of them are clear.

Foremost was to achieve "normalization" in Europe. The absence of a European peace treaty at the end of World War II had left uncertainty and potential (sometimes real) instability on the borders of the new Soviet empire. The Soviets sought western recognition of East Germany and acceptance of Soviet puppet regimes throughout East Europe, and detente gave them both.

Nuclear arms control also was a Soveit ambition. Through the 1960s, the history to the Soviet Union. The United States stayed well ahead of the Soviets in both the quantity and the quality of strategic arms. By the end of the 1960s the Soviets were catching up fast, but they apparently saw negotiated agreements as a useful means of controlling the Americans while allowing themselves to keep building weapons.

(This idea appealed to the United States, too, on the ground that nothing the United States could do unilaterally could prevent the Soviets from catching up, or from pushing the arms competition into ever more costly and dangerous cycles.)

There has always been an economic interest in detente for the Soviets, but its significance has never been clear. In this regard, 1969 was an important year for the Soviets too, as Robert Legvold of the Council on Foreign Relations noted in an interview. That year Soviet leaders began an unusually candid attempt to analyze the failures of their economy in the late 1960s.

By 1971, at the 24th Congress of the Soviet Communist Party, the leadership had adopted a new attitude on economic issues. They began to speak of an "international division of labor," implying that there were some things foreigners might be able to do for the Soviets that they couldn't do themselves. This departure from historic Soviet self-sufficiency was one of the signals of Moscow's interest in detente.

Some analysts believed that the Soviet desire for western capital and technology -- to compensate for Soviet failures and backwardness -- was central to their desire for detente. Other analysts regarded this as a fringe benefit for the Soviets. This debate cannot yet be resolved conclusively.

The significance of Soviet fears of China is less debatable. Clearly, the Kremlin leadership wanted to prevent the evolution of good relations between China and the United States and other western powers, and also to maintain good relations on the Soviets' western front to better deal with the Chinese threat, which provoked a hugh Soviet buildup in Asia in the late 1960s and early 1970s.

Finally, the Soviets saw detente as appropriate in light of "the changing correlation of forces" in the world, to use their oft-employed phrase. They apparently decided in the early 1970s that the "socialist camp" had so strengthened its international position, while "the imperialists" had so squandered their own, that they could deal with the West on a basis near enough to equality to be potentially profitable.

Perhaps the most important single statement of this view was an article published in the ideological journal Kommunist in the spring of 1973. It was written by Georgi Arbatov, the Kremlin's chief "Americanaologist." Though allowing for the possibility that reactionary forces in America could still disrupt the process, Arbatov argued that Americans needed detente to cope with the many serious problems they faced.

In effect, Arbatov wrote that the Soviet side could probably trust the Americans to pursue their own best interests, and those interests would push them toward better relations with the Soviet Union. America needs to slow down the arms race, reduce the danger of war and benefit from trade with the East, Arbatov wrote.

Altogether, it seemed, the Soviet Union decided early in the 1970s that it could best pursue its own security and internal development by seeking markedly better relations with the western powers. It was an idea that did not survive the decade in which it was born.