In a world of increasing turbulence, the United States and the Soviet Union face new risks of being drawn into conflict by miscalculation, specialists on both sides agree.

"One of the most serious challenges facing us," said Edmund S. Muskie in the closing days of his brief months as the successor to Secretary of State Cyrus R. Vance, is the "continuing challenge of reading Soviet intentions." It is a dilemma shared by all his predecessors. Soviet leaders complain even more aboutt their inability to discern where American policy is headed.

The Reagan administration hopes to reduce the chances for Soviet miscalculation of American intentions by drawing sharper lines to mark out vital American global interests. Many specialists favor that. Others fear that unless that effort is accompanied by joint plans for "crisis management," the two superpowers will become dangerously polarized, eliminating any opportunity to reconcile conflicting positions before they reach an uncontrollable stage.

There is little comfort in the recent record about the capacity of the two nations to foresee interactions that can confound both of them, even when they share overlapping objectives.

In 1979-80, each superpower contributed to destroying any hope for ratifying the centerpiece of seven years of diplomacy, the intended strategic arms limitation treaty, SALT II.Apart from the intense arguments in the United States over the nuclear accord itself, the pact was whipsawed by two extraneous developments: the American political furor over a Soviet "combat brigade" in Cube, and finally, by the Soviet invasion of Afghanistan which shattered the crumbling structure of American-Soviet detente.

That record, when looked at from the opposing sides, illustrates the great gulf in perceptions that divides the two nations.

The Soviet Union saw the dispute about its troops in Cuba as a deliberate provocation, part of an American "grand design" to postpone SALT ratification for domestic political purposes, and to stiffen the American terms for detente. In turn, the Soviet Union saw itself doubly justified in serving its own security interests, by sending its forces into Afhganistan to assure Marxist rule in that bordering nation.

Soviet leaders might well have decided to intervene in Afghanistan in any event; no outsider can be certain what course the Kremlin would have taken if it attributed higher costs to detente from its Afghanistan venture. What is clear is that each superpower badly misjudged the long-term repercussions of its actions on the other.

American reactions to the projection of Soviet-Cuban military force have been constantly underestimated in official Soviet thinking.

The Soviet Union was largely insensitive to the impact on Soviet-Cuban exploitation of military power in Africa, between 1975 and 1978. One consequence, the worst of all for the Soviet Union, was the intensification of cooperation between the United States and China to thwart the expansion of Soviet influence in Africa and other regions.

The establishment of full diplomatic relations between Washington and Peking on Jan. 1, 1979, marked not only the restoration of formal ties. As strategic consultation between the United States and China expanded the United States was shifting from its posture of equal balance between Moscow and Peking in the American-Soviet-Chinese triangle. The Soviet Union's two greatest opponents became increasingly aligned against it, despite the absence of any outright alliance.

By the time President Carter and Soviet President and Leonid Brezhnev signed the long-delayed SALT II pact six months later in Vienna, in June 1979, American-Soviet relations were under accumulated strain. From Vienna onward, in Soviet perpective, a failure to ratify the accord, after negotiations stretching over three administrations, would signify gross American default -- if not something more sinister.

The Carter administration was on notice that the nuclear accord would be fiercely contested in the Senate. But it was totally unprepared for the consequences of what was originally injected into the Senate hearings on July 17 as a relatively minor side issue: reports about "a recent build-up of Soviet combat troops in Cuba, perhaps a brigade." Soviet military personnel had been in Cuba since the 1962 Cuban missile crisis, when the force reached a peak of 40,000 men; but nothing like "a combat brigade" had been identified in the intervening years of greatly reduced Soviet force levels.

What developed is familiar enough on the American side. The Carter administration originally disclaimed evidence of any change in the Soviet military presence on the island, only to discover by satellite photography in late August what U.S. intelligence labeled a "Soviet combat brigade." The choice of words was devastating politically, although no evidence developed that the unit was new, or intended for combat.

The ensuing developments were complex for Americans to follow; in Moscow they began to take on the dimensions of a plot.

Before the Carter administration could coordinate its public position, Sen. Frank Church (D-Idaho), chairman of the Senate Foreign Relations Committee and up for reelection, announced confirmation of the existence of a Soviet combat brigade, called for its "immediate withdrawal," and added that failure to remove it would doom the SALT pact.

In an attempt to calm the domestic uproar without jeopardizing SALT, Secretary of State Vance announced that there were 2,000 to 3,000 Soviet troops, with tanks and artillery in a brigade formation in Cuba, in addition to 1,500 to 2,000 Soviet military advisers. While "elements of a Soviet brigade" may have been there since the early 1970s or longer, Vance said the United States "will not be satisfied with maintenance of the status quo."

That declaration was intended to give the administration flexibility to bargain out a compromise with the Soviet Union. Instead, the administration was caught between its political critics and Soviets inflexibility; it unwittingly had painted itself into a corner.

In 1962 Soviet strategists had sworn "never again" to allow their nation to be humiliated as it was that year, when the Soviet Union was forced to withdraw its nuclear missiles from Cuba under the threat of overwhelming American military attack. China seized on the Soviet plight to mock its ideological rival for "adventurism" in sending its missiles into Cuba, and for "capitulationism" in ruling them out.

It took the Soviet Union a decade of extremely costly military expansion to cancel out the strategic advantage that the United States held at the time of the missile crisis. For the Soviet leadership, the new American outcry over a Soviet brigade in Cuba was a deliberate reopening of its deepest wound in the superpower rivalry. Rejecting any change in the "status quo" in Cuba, the Kremlin doomed Vance's attempts to work out a face-saving compromise with Soviet Foreign Minister Andrei Gromyko to quiet the uproar in the United States.

The United States, Soviet planners suspected, either was attempting to extort a wholly new price for SALT, of it was engaged in a devious change of policy. In Soviet perception, an American "grand design" began to fall into place.

As described by Soviet sources in Moscow at the time, their version of the American "design" -- which Carter administration officials found "ludicrous" -- included the following elements:

The United States deliberately had "concocted" a new imaginary "Soviet threat" in Cuba to give the Carter administration "a pretext" to sidetrack ratification of the SALT accord until the 1980 presidential election.

Why? To enable President Carter tomove to the political right in order to meet the challenge raised from the direction by Ronald Reagan. Carter therefore could repeat the pattern followed by President Ford in the 1976 presidential primary elections campaign. With Reagan as his opponent, Ford broke off the SALT negotiations early that year, dropped "dente" from his vocabulary and substituted "peace through strength."

Simultaneously, the United States was moving on two other fronts toward a more militantly anti-Soviet policy.

Vice President Mondale traveled to Peking at the end of August to intensify the coordination of anti-Soviet policy with China.

The United States was now seeking to induce its Western European allies to accept the deployment of new missiles (108 Pershing II ballistic missiles, and 464 ground-launched cruise missiles) on their territory, with ranges of 1,200 to 1,500 miles -- long enough to reach deep into Soviet territory.

No American can be certain to what extent the Soviet leadership truly believed that such a design actually existed in Carter administration planning. But it is significant that this pattern of intentions was being attributed to the Carter administration by Soviet sources as early as mid-September 1979, more than three months before the Soviet Union sent its troops into Afghanistan. After the Afghanistan invasion, the alleged American "design" was expanded by added Soviet grievances.

The events which went into the Soviet "grand design" looked totally different from an American perspective:

The dispute over a Soviet brigade in Cuba was as much a surprise to the Carter administration as it was to the Soviet Union. President Carter wanted to save the nuclear agreement not abandon it -- although his political fate did turn out to be a duplicate of President Ford's, who lost the 1976 election to Carter.

Mondale's trip to China had been announced long before the first hint of dispute over a Soviet brigade in Cuba, and was unrelated to that episode.

The plan to deploy American Pershing missiles and cruise missiles in Western Europe similarly came out of a different context -- to counter the deployment of Soviet SS20 missiles and Backfire bombers in Eastern Europe. The American missile plan, later confirmed by the foreign ministers of the North Atlantic Treaty Organization at their December 1979 meeting, would have drawn bitter Soviet opposition in the most placid American-Soviet climate.

In assembling an ominous design out of these separate actions, Soviet officials had done what planners on both sides do constantly: seek out possible connecting links in the adversary's actions, to determine if there is a predictable pattern of actions or intentions.

If a planner looks hard enough at an adversary's actions from a "worst case" premise, that is what usually emerges. There are times, of course, when the "worst case" assessment proves to be justified -- or even understimated.

That was what occurred in the American assessment of Soviet intentions, in the months leading up to the invasion of Afghanistan. The two sequences, the dispute over the Soviet brigade, and Soviet preparations for military action in Afghanistan, over-lapped in the autumn of 1979.

President Carter was obliged to announce on Oct. 1 that the Soviet Union refused to go beyond assurance that its military units in Cuba would remain in a "noncombat status." Hearings proceeded on SALT II, but with the Carter administration under a new cross fire of charges that it had surrendered abjectly to Soviet intransigence. At the same time, American intelligence was sounding an alarm about Soviet intentions in Afghanistan.

In mid-September, the leader of Afghanistan's Marxists who had seized power in 1973, Nur Muhammad Taraki, a Soviet favorite, was slain in what western intelligence later reported as a backfired Soviet attempt to oust Taraki's rival, Prime Minister Hafizulah Amin. Instead, Taraki, Moscow's favorite, was killed in a shootout; Amin survived in power.

By late September, American intelligence reported danger of a major "Soviet military involvement" in Afghanistan to keep that nation in the Soviet bloc. A rebellion was spreading across Afghanistan, with several thousand Soviet military personnel trying to help contain it. The early American intelligence reports proved to be quite accurate in assessing the choices that confronted the Soviet leadership, but they expressed doubt that the Soviet Union would risk massive intervention.

As summarized in a study circulated to members of the Senate Foreign Relations Committee, dated Sept. 24, 1979, U.S. intelligence cautioned that "events . . . may force Moscow into choosing between allowing a neigboring Marxist regime to be overthrown or substantially increasing its commitment to the regime."

Among the reasons cited as "pushing Moscow toward deeper military involvement" in Afghanistan were: the fulfillment of Russian ambitions since Marxist days "to expand Moscow's influence into Afghanistan;" the desire to have a disciplined Marxist state on the Soviet border as a "pro-Soviet factor in the regional politics of Pakistan, India and Iran," and the prospect of acquiring "an important firebreak against perceived Chinese encirclement" of the Soviet Union.

On the opposite side, arguments listed as inducing Soviet caution about deeper involvement in Afghanistan included: "mistrust of Amin's judgment and durability;" the possibility of becoming bogged down in a Soviet-Vietnam situation," adverse world reaction, especially from Moslem nations in the region, and "the possibility of American counteraction elsewhere," with the danger of "tipping the balance against SALT II ratification." The Soviet Union, however, already had discounted the SALT cost.

With that factor undetected, the Senate intelligence summary concluded that a Soviet airborne division near the Afghanistan border could be used "to protect/evacuate 5,000 to 6,000 Soviet officials and dependents" or, alternatively, "to intervene massively to support Amin." On the information then available, the report estimated that the Soviet Union would choose the more modest of those alternatives.

The situation in Afghanistan deteriorated rapidly, however in the following weeks. At the same time, the United States became engulfed in what a dismayed Carter administration saw as "a crescendo of crisis."

On Nov. 4, 1979, the American Embassy was seized in Tehran, with the capture of American hostages plunging the Carter administration into its most agonizing ordeal and raising fear that the Soviet Union would exploit the tide of anti-Americanism in the region to imperil the West's oil lifelines in the Persian Gulf. Then, on Nov. 21, Pakistani mobs attacked and burned the American Embassy in Islamabad.

Afgahnistan, sandwiched between Iran and Pakistan, was overshadowed on the American scale of priorities just as it turned into the Kremlin's dominant objective in the region.

By late November, U.S. intelligence reports showed an increasing build-up of Soviet personnel and equipment on the Soviet side of the Afghanistan border. The United States, in early December, began sounding diplomatic and public warnings about the Soviet military preparations. On five occasions in December, up to the day of the Soviet invasion, the United States cautioned the Soviet Union, in discussions in Washington and in Moscow, that intervention in Afghanistan would have "serious consequences" on the two nations' relations.

But there was no "or else" message. "We did not specify what action we would take," it was reported later by Marshall D. Shulman, special adviser on Soviet affair to Secretary of State Vance. The Carter administration had no effective counterweight to apply.

The State Department acknowledged in a letter to a House subcommittee on April 10, 1980, submitted by Shulman, that "the weight of our views was diminished by the frayed state of U.S.-Soviet relations and the fact that we had already invoked the prospect of damage to U.S.-Soviet relations and SALT on several other issues." The SALT argument was brushed aside by the Soviet Union. Another senior American official, in private, expressed the Soviet attitude more bluntly: "They told us, in effect "'Bug off.'"

Even then, the magnitude of the Soviet plunge into Afghanistan, which began on the evening of Dec. 24 with a massive airlift of airborne troops and other units into the capital of Kabul, and continued for three days in its initial stage, startled many American policy-makers. Prime Minister Amin, the Soviet Union insisted, had called for Soviet aid. On Dec. 27, after Soviet troops seized key points in Kabul, Amin and members of his family were executed.

"Radio Kabul" -- actually a transmitter on the Soviet side of the border, American intelligence reported -- announced that day that Amin had been convicted of "crimes against the state" and executed by a "revolutionary tribunal," with Babrak Karmal installed to replace him as president. American officials said when the announcement was made, Karmal, an Amin rival who had been sent into political exile in Eastern Europe, actually was being rushed back to Kabul by the Soviet Union.

By eliminating Amin, the Soviet Union destroyed any plausible international premise for its presence in Afghanistan, as evidenced by overwhelming condemnation of its action outside the Soviet bloc. Unlike the Soviet military interventions in Hungary in 1956, or in Czechoslovakia in 1968, in Afghanistan the Soviet Union had reached far beyond its recognized security zone to impose its authority on an unaligned Moselm nation.

". . . This action of the Soviets," President Carter declared, "made a more dramatic change in my own opinion of what the Soviets' ultimate goals are than anything they have done in the previous time I've been in office." That public expression of shock brought ridicule from the president's critics for his naivete. The Soviet invasion, however, while far less surprising to hardened veterans of American-Soviet competition was an unprecedented extension of Soviet military power.

Many Soviet sources conceded that, in private. They acknowledged that the Soviet Union had gone beyond anyone's interpretation of detente, but claimed justification for the Soviet action in the imperatives of Soviet security, following American default on its commitments to detente.

It is the official Soviet position that all its actions in Afghanistan were fully sanctioned by international law, in response to pleas for aide from a nation endangered by foreign agents: "Tens of thousands of mercenaries, armed with foreign arms . . . put in the hands of saboteurs by American and Chinese instructors," and "even specialists in subversion . . . from Egypt," the Soviet Union claimed, operating from bases in Pakistan.

"In effect," Soviet President Brezhnev charged, "imperialism together with its accomplices launched an undeclared war against Afghanistan."

Some western specialists believe that the Soviet Union was genuinely fearful that the United States and China might acquire a foothold in Afghanistan, with Amin developing into an Asian version of Yugoslavia's late Marshal Tito.

The Soviet Union's resort to massive force in Afghanistan was so crude, however, and its rationalizations so weak, that it has made palpably little headway in convincing the nations of the world of the righteousness of its cause. That was demonstrated again last November, nearly a year after the Soviet drive into Afghanistan, by a 111-to-22 vote in the United Nations General Assembly demanding a withdrawal of "foreign troops" from Afghanistan.

Afghanistan inevitably produced in American perception a far more menacing Soviet "grand design" than the design which the Soviet Union attributed to the United States.

"The implications of the Soviet invasion of Afghanistan," Carter told Congress last January in his State of the Union address, "could pose the most serious threat to world peace since the Second World War."

He warned that "an attempt by any outside force to gain control of the Persian Gulf region will be regarded as an assault on the vital interests of the United States of America, and such an assault will be repelled by use of any means necessary, including military force."

To many world diplomats, both declarations represented excessive alarm. Nevertheless, a year later, the threat to the West's sources of oil which hangs over the Persian Gulf is not imaginary.

The continuing conflict between Iran and Iraq which subsequently developed can still spill over and entrap both superpowers, regardless of what occurs in Afghanistan. Whether the Soviet Union ever had a "grand design" in the area -- which it adamantly denies -- the presence in Afghanistan of 85,000 Soviet troops still nourishes high American suspicions about Soviet intentions. In either case, this leaves both superpowers exceptionally vulnerable in the volatile region to miscalculations which can draw them into confrontation.