As Sen. Richard Stone (D-Fla.) arrived at the ornate Senate Caucus Room for a Foreign Relations Committee hearing at 10 a.m. last July 17, a senatorial aide pulled him aside to impart a fascinating tip.

"I've been picking up reports on a recent buildup of Soviet combat troops in Cuba, perhaps as much as a brigade," said the aide, whom Stone will not identify.

In response to the expected question, the aide announced, as Stone recalled it, that the information did not come from a classified official paper, and therefore "you don't have a classification problem" about sounding a public alarm.

In the course of the hearing, supposedly addressed to the strategic arms limitation treaty (SALT II) on nuclear weapons, Stone pointedly inquired of the witnesses, retired members of the Joint Chiefs of Staff, about the impact of the hypothetical Soviet introduction of "as much as a brigade of combat troops in Cuba.

The press corps perked up at this new element in the dull SALT story. Off the record and off camera, Stone also had a private exchange that morning with John Carbaugh, a staff aide to anti-SALT Sen. Jesse A. Helms (R-N.C.).

Carbaugh had heard reports of his own about a Soviet combat force in Cuba. Within a few hours, Carbough passed his tip along a ABC Television, which began an independent investigation.

These small transactions in mid-July ballooned into a large-scale national and international controversy late in August, leading to a diplomatic confrontation with the Soviets in September and President Carter's televised address about Soviets troops in Cuba on Oct. 1.

Whatever the view of the importance or importance of the Soviet "brigade," whether insiders or outsiders to the Carter administration, whether Carter friend or Carter foe, nearly all those familiar with the details of this latest Cuban crisis agree that it was badly mishandled.

Accidents, miscalculations and, much more appalling to old hands, the seeming lack of any sophisticated calculation, contributed to the result; which was described by a British newspaper as "a self-inflicted technical knockout."

Among the other contributing elements:

An administration still divided at the top on Soviet policy after 2 1/2 years in office, even as the pending SALT II generates a national debate about the nature and intentions of the Russians.

The present Washington fishbowl in which official secrets quickly leak or are leaked by contending factions, forcing premature announcements and decisions.

Members of Congress and congressional aides who possess the knowledge, power, maneuver skills and increasingly, the inclination to do their own thing in U.S. diplomatic and military affairs.

The inherent ambiguity of the intelligence and misleading character of the term, "Soviet combat brigade," which created a widespread and erroneous impression that something fundamentally new and threatening had been found.

The results of all this -- to create vast public concern and confusion, to endanger the strategic arms treaty, to jeopardize U.S.-Soviet relations -- did not emerge overnight. They developed step by step since Stone brought the issue to light on July 17.

Soviet troops in Cuba and U.S. intelligence awareness of them go back many years, but a July 12 report by the highly secret National Security Agency marked the beinning of a new and troublesome phase.

The NSA report suggested that a Soviet brigade organization, separate from known military adivsers or training elements, had been present in Cuba for several years.

Although there was no firm conclusion and no reference to the word "combat," the report touched off alarm bells in high places and led to a new increase in U.S. surveillance of Cuba.

Only five days later Stone had his tip. After attracting the interest of the media at the morning hearing on July 17, the Florida senator took his inquiry to a closed-door Foreign Relations Committee hearing with top Pentagon and intelligence officials which, by coincidence, had been scheduled for that afternoon.

Defense Secretary Harold Brown and the chiefs of U.S. intelligence agencies gave "an equivocal answer but not a flat denial," according to Stone, and then told a secret impromptu hearing of the NSA findings up to that point. Stone made it clear he would take his suspicions, but not the details of the briefing, to television cameras waiting for him outside.

The committee leadership, concerned about the potentially explosive controversy, asked for and obtained a public statement drafted by Brown and the intelligence chiefs on the spot to put the matter in perspective.

The statement issued in the names of Chairman Frank Church (D-Idaho) and the senior Republican, Sen. Jacob Javits (N.Y.), said there was "no evidence of any substantial increase" in Soviet military presence in Cuba over several years. It also said "our intelligence does not warrant the conclusion" that any "significant" Soviet forces, other than the long-known military advisory group, was present in Cuba.

The statement gave no hint of the intense internal study and debate on the issue, which only two days later, on July 19, produced a secret CIA finding that a brigade headquarters or structure, at least, was in Cuba separate from an advisory group.

The basis for this finding was simple and persuasive: Soviet officers and men had been overheard repeatedly to refer to a brigade headquarters, or "brigada." There was no agreement in this compromise finding, negotiated by CIA Director Stansfield Turner, on the organization, personnel strength or mission of the shadowy entity.

Turner was briefing Secretary of State Cyrus R. Vance on the finding late on July 19 when they were confronted by ABC Television's inquiries.

Diplomatic correspondent Ted Koppel was informed that a "command structure" adequate for a brigade had been confirmed, but the charge of a brigade itself was rejected.

The next day Koppel broadcast a report attributed to undisclosed congressional sources that "a brigade of Soviet troops, possibly as many as 6,000 combat-ready men, has been moved into Cuba within recent weeks." He noted the administration denials.

Despite the new development in intelligence and confirmation of the "command structure," the administration continued to use the cautiously worded denials of the July 17 Church-Javits statement, notably in a letter from Vance to Stone dated July 27.

When the letter became known it caused a furor among intelligence professionals. Some of them considered it "a lie" and determined to make sure that the true situation would reach the public.

Another step into the thicket came nearly a month later, after U.S. intelligence had obtained clear satellite photographs of Soviet troops acting as a unit, complete with tents, tanks and artillery, on field maneuvers at a prearranged time and place a few miles west of Havana's airport.

Based on the new evidence, the CIA's National Foreign Assessment Center issued a coordinated intelligence finding Aug. 22 that the previously identified structure was a "Soviet combat brigade." Beyond the important conclusion, the choice of words was crucial in what was to come.

The word, combat, had not been used in the findings before, but there is no indication that its threatening connotations and political implications were appreciated, or even examined, at the time.

Intelligence officials later explained that the "Soviet combat brigade" was so described to distinguish it from a training outfit. Once the words had been repeated in internal documents, with wide circulation and even public statements, "we can't back off," an inquiring official was told.

In fact, there is no sign that the Soviet force in Cuba had ever engaged in combat, and no indication that its mission is to be prepared to do so. There is no airlift or sealift attached to the unit to permit speedy "combat" deployment. There is no plausible "enemy" for the small force to do "combat" against.

According to those who have examined the evidence closely, it is more accurate to say that the Soviet force appears to have some role other than training and advising Cubans. (It also may have that role from time to time.) Even today, U.S. intelligence has not concluded what the real mission or missions are. Engaging in combat is not considered to be among the most likely possibilities.

The words, "Soviet brigade" or "Soviet nonadvisory brigade" or even "Soviet infantry brigade" would have been much more accurate, and much less alarming. But it was left to the sophisticated minds of the "wise men," the former high officials summoned to the White House on the eve of Carter's Oct. 1 address, to spot the semantic significance of the "Soviet combat brigade" and challenge it frontally. By then the damage had been done.

The coordinated intelligence finding of Aug. 22 presented the government with a hot potato at an awkward moment, with most top officials out of town or on vacation. The first inclination was to delay.

President Carter was informed of the findings Aug. 23 as he sailed down the Mississippi aboard a paddlewheel boat. Back in Washington, an interagency meeting of second-level officials at the White House concluded that the brigade reflected a long evolution rather than a sudden change in Cuba, and that it did not have a "short time fuse."

They hoped that major action would be delayed until after Labor Day, when Congress and the main administration figures would be back.

A telephone call from the Washington Bureau of Aviation Week, a noted vehicle for leaks from the Pentagon and defense contractors, changed all that. On Thursday morning, Aug. 30, the magazine asked the State and Defense department press spokesman about reports of Soviet combat troops in Cuba, and told the officials that a story on the matter was going to press that night.

The Aviation Week query touched off a near panic among high officials, but in fact it was a bluff. The magazine's information was considered neigher solid enough nor important enough by its own editors to warrant publication in the issue that went to press that day. Lacking confirmation from the government, Aviation Week printed nothing about the Soviet brigade in its post-Labor Day issue.

Government officials, who assumed that Aviation Week was printing a complete version, decided to inform senior members of Congress immediately and to prepare an official announcement. This led to emergency calls late on Aug. 30 to eight ranking members of Congress, who were scattered throughout the world on the eve of Labor Day.

The decision by one of them, Frank Church, to make the news public in stark fashion set the terms of public dialogue. After informing Vance that he was going to make a statement -- but not what he intended to say -- Church summoned reporters to his living room in Boise and announced government confirmation of a Soviet brigade of ground combat troops in Cuba. Church demanded their "immediate withdrawal," and later said SALT II could not be ratified unless this were done.

In an effort to step back from Church's call for Soviet withdrawal, a negotiating objective considered impractical under the circumstances, Vance and the State Department fell back on the vague statement that, for the United States, "the status quo is unacceptable."

This was approved at a White House meeting Sept. 4 and put forward by Vance the next day in a press conference and by the president on Sept. 7.

No attempt was made to explain to the public until late in the affair that an unacceptable status quo could be altered by U.S. compensatory actions or that some situations which are unacceptable, in diplomatic language, persist nevertheless.

A powerful senator picked up the problem with the official language right away. When Vance completed a private briefing the day of his news conference, this close friend of the administration expressed surprise, in a tone of disapproval, of the "status quo" language.

It implies you are going to be able to do something about the Soviet brigade, the senator told Vance, thus setting up a public perception of failure if this does not happen.

The issue dominated the American press, was a major and growing impediment of SALT II, and had been the subject of Church's announcement, a State Department announcement, Vance's new conference and a public announcement by Carter. Yet negotiations still had not begun with the Soviets. Vance was increasingly desperate for the return of Soviet Ambassador Anatoliy F. Dobrynin.

The Soviet offical was still in Moscow, where his father was dying in a hospital and his mother gravely ill in the same institution.

Despite the poignant personal considerations, Vance felt Dobrynin's presence essential to the chances, such as they were, for a diplomatic settlement. Messages were dispatched through the Soviet embassy in Washington and the U.S. embassy in Moscow, and finally an appeal was made by Vance direct to Soviet Foreign Minister Andrei A. Gromyko.

Gromyko telephoned Dobrynin to ask him -- but not order him -- to return to accommodate Vance. The envoy was on the next plane, which took off shortly before the second of his parents died.

The Soviets position, which became clear on Dobrynin's return, had been foreshadowed by a message delivered by Deputy Ambassador Vasev several hours after Vance's news conference. The Soviets insisted that their force was a "training center" that had been in Cuba since 1962 and had not changed since in either the number of its personnnel nor its function.

The Soviets were at the same time angered, puzzled and suspicious. They could not understand why the issue had suddenly emerged, and took the position that they had done nothing to cause this "manufactured" crisis.

Dobrynin, like his superiors in Moscow, proved unsympathetic. Either U.S. intelligence was so bad it did not spot the Soviet force in 17 years, or it was so slipshod that it failed to inform those at the top of the U.S. government -- in either case no affair of the Kremlin, he said.

He asked two questions: Is the force a threat to the United States? Is it s violation of the previous U.S.-Soviet understandings about Soviet activities in Cuba. In both cases the U.S. answer was no.

In these circumstances the Soviets were willing to supply information about their Cuban foces and later, in what they called a unilateral gesture to Washington, to supply certain "clarifications" about the role of their troops.

But they were unwilling to take any action to change the existing physical situation of the Soviet force on the ground, as suggested by the United States. And they have not agreed to do so in the future, though neither is this foreclosed.

In the midst of Vance's attempt to convince the Soviets to make at least face-saving concessions, an "or else" note crept into public utterances and private briefings at the White House. This generated confusion, which still persists, about retaliatory measures against Moscow for failure to remove or dissolve the brigade.

Presidental assistant Zbigniew Brzezinski, who hinted at retaliatory action on several occasions, took as his text a sentence in the presidential statement of Sept. 7: "We do have the right to insist that the Soviet Union respect our interests and our concerns if the Soviet Union expects us to respect their sensibilities and their concerns."

Brzezinski spoke Sept. 21 and on other occasions of "the principle of reciprocity" and of unspecified "consequences" for U.S.-Soviet relations if negotiations fail to settle the issue.

On Sept. 23 columnist James Reston of The New York Times, whose access to top officials is legendary, described a set of potential consequences apparently reflecting option papers under consideration.

These included "countermeasures along the borders of the Soviet Union," a stepup in U.S. propaganda and economic appeals to communist countries in Eastern Europe and even the Ukrainian minority within the Soviet Union, and an increase in U.S. "economic, technological and, particularly, military aid to Peking," Moscow's arch rival.

A battle raged within the U.S. government about countermeasures to be taken. Who won and to what extent is in doubt.

The U.S. compensatory measures announced in Carter's Oct. 1 address were limited in symbolic or nonmilitary displays in the Caribbean region, and increases in worldwide U.S. alertness or deployments which had previously been scheduled. The speech was devoid of anti-Soviet retaliatory measures.

State Department officials have told reporters that anti-Soviet options were not approved by Carter. These officials deny the existence of a "hidden agenda" of authorized retaliatory actions.

Hints from the White House run the other way. Some reporters have been told that the leaked announcement of Brown's coming trip to China flowed from U.S. displeasure about the Soviet brigade, and that the substance of Brown's dealings in Peking were likely to be affected. There is talk of three or four "associated measures" deliberately chosen but not announced at the time of the presidental speech. How much of this is substance and how much is smoke is still unclear.

It is easy to say, in hindsight, how the issue of Soviet troops in Cuba could have been more effectively handled under other circumstances.

If the administration had been either silent or more candid in the early stages. If the intelligence had been more definitive, and the description of the findings more precise. If there had been time and the means for quiet negotiations with the Soviets before the issue became public. If congressional leaders had been quietly supportive rather than outspoken. Is some public rhetoric had not supported hopes for an unattainable diplomatic settlement, and other rhetoric had not fed expectations, in the midst of the negotiation, of hardline anti-Soviet action. If the whole thing had not developed while the top rank of official Washington, and the Soviet ambassador, were out of town.

What is impossible to say is whether any or all of this would have changed the final result in which the Soviet force, whatever it is, remains in Cuba and the U.S. government and public remain concerned and unsatisfied. i

One certainty, in the opinion of veteran observers, is that the Carter administration's Cuban crisis was mismanaged. Worse than that, they fear that it was not managed at all.