One reason for Secretary of State George P. Shultz's success in government, business and academia is his exceptional skill as a team player who keeps his personal views hidden. But on at least two subjects, the normally taciturn Shultz has expressed himself in startling fashion.

Shultz's attempts to force an American response to terrorism and his unyielding opposition to polygraph tests of senior officials show the secretary of state at his most determined. Hitherto unreported details of both episodes provide clues to the man behind the public mask who has been at the helm of U.S. diplomacy for the past 3 1/2 years.

By all accounts, Shultz's strong views on terrorism grew out of the failure of U.S. policy in Lebanon, his most traumatic foreign policy crisis. The Oct. 23, 1983, suicide bombing of U.S. Marine headquarters destroyed Shultz's efforts to achieve a negotiated withdrawal of Israeli and Syrian forces from Lebanon. And frustration in Lebanon contributed to a reversal of Shultz's original leanings on Middle East issues.

During the 1980 presidential campaign, Shultz complained to friends that candidate Ronald Reagan, whom Shultz supported generally, was taking an unbalanced, pro-Israeli position on Mideast questions. After being named secretary of state in June 1982, Shultz called publicly for international action on the Palestinian issue, a position distasteful to the Israeli government of Menachem Begin. Shultz's first, and still his most daring, diplomatic move was authorship of this Sept. 1, 1982, "Reagan plan" for Middle East negotiations. It was welcomed by King Hussein of Jordan, who was consulted in advance, and rejected by the Israeli government, which was not.

Today, in contrast, Shultz is considered the most pro-Israeli figure at the top rank of the Reagan administration. He and the Arabs have been deeply disappointed in one another. And in the wake of failure in Lebanon, Shultz is exceedingly cautious about any U.S. leadership role in a Middle East peace process.

In 1982 Shultz advocated sending U.S. Marines on a peacekeeping mission to Lebanon, originally to ease the withdrawal of the Palestine Liberation Organization and later to symbolize the U.S. commitment to a peaceful, negotiated solution there.

As the Marines came under increasing fire in the summer and fall of 1983, Shultz advocated use of U.S. military power, including naval gunfire and air strikes, against those threatening them. In this he was repeatedly pitted against Defense Secretary Caspar W. Weinberger and the Joint Chiefs of Staff, who resisted the use of U.S. power and wanted the Marines to come home.

As sponsor of the troop presence and as a proud ex-Marine who often wears a Marine Corps necktie, Shultz was angry and distraught when a suicide truck-bomber killed 241 U.S. servicemen on Oct. 23. In the aftermath, Shultz was a principal advocate of a retaliatory bombing attack on a pro-Iranian Shiite Moslem group identified by the Central Intelligence Agency as involved in the attacks on the Marines and on French troops the same day.

"A beautifully coordinated agreement with the French" was worked out for a joint air strike against a headquarters of the militant Shiites near Baalbek, according to a former U.S. official involved in the planning. Reagan approved a joint raid, but at the last minute "the secretary of defense just pulled out of it," the former official said.

An associate of Weinberger said the defense secretary, who was opposed to the air strike, kept raising questions until French warplanes made the attack alone -- and without much effect -- on Nov. 17.

This experience was followed by Reagan's February 1984 decision to withdraw the Marines, made over Shultz's protest while the secretary was out of the country. Shortly thereafter Shultz began to campaign for forceful responses to state-supported terrorism.

Along with national security affairs adviser Robert C. McFarlane, a kindred spirit and fellow former Marine, Shultz was a strong proponent of National Security Decision Directive 138, signed by Reagan April 3, 1984, establishing a general U.S. principle of taking preemptive and retaliatory strikes against terrorists.

But Shultz found that it is one thing to have a presidential paper establishing policy and quite another to see it carried out, especially in the face of Pentagon opposition. The very day the directive was secretly signed Shultz made his first public address suggesting "preventive or preemptive action against known terrorist groups."

In the 22 months since, Shultz has carried on a highly unusual public campaign, making ever stronger calls for antiterrorist action through military muscle. First, he argued that the use of force was necessary. Then he declared it to be moral. Last month he pronounced it legal under international law.

A motive of Shultz's campaign was "to get the American people on board" because he has "no confidence in the Pentagon's ability to define the role of force, and he is trying to push it to do that," said a source who has had an unusually intimate view of State-Defense interaction in the Reagan administration. Time and again -- on terrorism, arms control and Central American issues -- "Cap Weinberger just wouldn't turn loose of a policy even when the president decided what it should be," this observer said. He added that Reagan, faced with guerrilla sniping in his administration, "won't enforce" his decisions because "he is torn by lack of conviction on policy and by loyalties" to each of his contending Cabinet members.

Administration insiders said Reagan's two most notable uses of military power, the U.S. invasion of Grenada and the interception of an Egyptian aircraft carrying terrorists who had attacked the cruise ship Achille Lauro, were made possible by special circumstances that enhanced the roles of Shultz and McFarlane.

In the case of Grenada, Shultz and McFarlane spent several crucial predawn hours alone with the president during a golfing weekend in Augusta, Ga. After that meeting, Reagan talked to Weinberger and others in Washington by telephone. By then Reagan was already "very firm" in his decision to go ahead, said a participant in the discussions. "Grenada never would have happened if Shultz and McFarlane had not been with Reagan out of Washington," another official said.

In the case of the aircraft interception, which Shultz strongly favored, McFarlane is credited by insiders with conceiving the idea and persuading the president to adopt it. Weinberger, who was returning from Canada as the action was being planned, was overheard by a ham radio operator as telling Reagan on an open radio line that he had just learned of the plan and had reservations.

Asked about his public campaign for forceful responses to terrorism, Shultz said in an interview, "I have been speaking very much for the president. I meet with him frequently, I listen to him carefully, I think I know his thinking and I don't ever make speeches that I think are at odds with what he thinks." Shultz conceded that he has differences with Weinberger on terrorist issues, but added that "broadly speaking, we both recognize the importance of the problem." Polygraph Policy Dispute

The story of Shultz's most celebrated public outburst -- his refusal to accept a presidential directive ordering wide use of polygraph tests -- begins more than two years ago.

Shortly before noon on Sept. 14, 1983, White House deputy chief of staff Michael K. Deaver entered the Oval Office to find Edwin Meese III (then White House counselor) and William P. Clark (then White House national security affairs adviser) in an intense and apparently confidential conversation with Reagan about a paper they wanted him to sign. The paper, Deaver discovered, would have authorized the FBI to use polygraphs to investigate top officials who were privy to highly classified decision-making about Lebanon.

Two days previously, on Sept. 12, NBC News had reported that Reagan was secretly considering U.S. air strikes against Syrian positions in Lebanon where U.S. Marines were being shelled heavily. Meese and Clark were furious at the leak and determined to identify the culprit.

Deaver described the Oval Office scene he had encountered to James A. Baker III (then White House chief of staff) while the two were driving to lunch at the Madison Hotel. According to a later account, Baker was so alarmed that he ordered the car back to the White House, where Baker and Deaver barged into a luncheon meeting of Reagan with Shultz and Vice President Bush.

Shultz and Bush were startled to learn of the plan and, like Deaver and Baker, they criticized any requirement that top officials submit to polygraphs. If asked to prove his veracity with a polygraph, Shultz declared, "Here's a secretary of state who isn't going to stay."

After angry confrontations between proponents and opponents of polygraphs, Reagan modified his order and eliminated polygraphs from the FBI's leak investigation, which never discovered the source of the disclosure to NBC.

Those events seem to have been either forgotten or ignored last summer, when the National Security Council was considering counterintelligence measures against spying by the Soviet Union and other countries. By this time Meese, Clark, Baker and Deaver had all left the White House, though Shultz remained as secretary of state and Meese had become attorney general.

One proposal called for extensive use of polygraphs to screen U.S. government officials with access to highly classified information. The measure was favored by CIA Director William J. Casey, whose agency has routinely used polygraphs for years. Weinberger was "no big fan" of lie detectors, but when he discovered Shultz's opposition, the defense secretary "fell in love with polygraphs," one involved official said.

The proposal to extend the use of polygraphs to the State Department and elsewhere was discussed last Aug. 7 in the National Security Planning Group, a highly confidential committee of the National Security Council. Shultz, according to participants, raised his deeply held objections during the meeting and left with the impression that the issue was unresolved.

What he had heard worried Shultz, however. It was simply unthinkable to him, according to aides, that trusted policymakers of the government should be wired for polygraph interrogation. On matters of personal integrity, Shultz can be relentlessly stubborn, as President Richard M. Nixon discovered to his anger in 1972 when then-Treasury Secretary Shultz flatly refused to order Internal Revenue Service audits of Nixon's political enemies.

Shultz was also aware of evidence that lie detectors can be misleading, and can be "beaten" by trained spies. He commissioned State Department Legal Adviser Abraham D. Sofaer to write a paper on polygraph shortcomings and sent it to Reagan to support the objections he had expressed at the Aug. 7 meeting. State Department sources said there was no sign that Reagan read or received the memorandum.

Shultz heard no more about the issue until receiving from the White House the text of National Security Decision Directive 196, which was signed by Reagan Nov. 1. In one paragraph of this five-page document, Reagan established as government policy the use of polygraph examinations for "all individuals" with U.S. clearances for access to certain types of highly classified information. This would have applied to at least 4,500 officials at the State Department, including Shultz, and more than 177,000 officials or contractors at Defense and in other departments.

When the polygraph portion of Reagan's decision circulated at State, an aide reported to Shultz that quite a few senior officials were threatening to resign if forced to submit to a polygraph. Shultz snapped, "And I'm one of them."

Shultz was in Europe in mid-December when the Los Angeles Times broke the story of Reagan's order. Questioned by reporters, Shultz declined to discuss it while abroad, saying the polygraph issue was "a domestic question." A few hours after his return on Dec. 18, Shultz discussed the matter privately with Reagan in the Oval Office.

The next day, however, Shultz told reporters he would resign if forced to take a polygraph. Speaking slowly and deliberately as television cameras whirred, the secretary announced, "The minute in this government I am told that I'm not trusted is the day that I leave." With that he left the room, where silence was followed by uncharacteristic cheers from some reporters applauding Shultz's outburst.

The statement seemed to leave Reagan with a choice between his polygraph directive and his secretary of state. According to a senior White House official, Reagan did not recall that the Nov. 1 directive he had signed contained a order for extensive polygraph tests. The president reportedly told a top aide, "Give me a reading, what does that damn thing actually say? Let's go back and see, what am I doing here?"

After meeting with Shultz Dec. 20, Reagan approved a White House statement that seemed to water down the directive, saying he had decided polygraphs would be required on a government-wide basis only as "a limited though sometimes useful tool when used in conjunction with other investigative and security procedures in espionage cases." A senior White House official said that was intended to permit the CIA and other secret agencies to use polygraph examinations "as a prelude to employment," but not to require polygraph tests as a screening device elsewhere in government.

A National Security Council spokesman said a few days ago that the Nov. 1 directive "has not been changed," adding that plans for enacting the directive remain under study. Shultz, however, points to the Dec. 20 White House statement as the last word. "I found the statement entirely satisfactory," he said in an interview. "As far as I'm concerned, that's the policy." Future in Academia

After 3 1/2 years, Shultz at times seems weary. Like other secretaries of state, he appears to have been exhausted by the long hours, the heavy pressures and abundant criticism that seem to come with the exacting job.

Those close to Shultz at State pricked up their ears in December when Stanford University in California announced that Shultz had accepted the newly endowed Jack Steele Parker professorship of international economics in the Graduate School of Business. Shultz taught at Stanford before becoming secretary of state, and in official biographies he listed his Stanford professorship before his concurrent job as president of the giant Bechtel Corp. Shultz still has a residence on the Stanford campus and is expected to return there when he leaves government.

"Professor Shultz is on leave from the university," said Stanford's Assistant Provost Noel Kolak. She said Shultz has given no indication when he might lay down the stewardship of U.S. diplomacy and return to the chalk and blackboard of academic life. Whether that will be before the end of the Reagan term in January 1989 is yet another secret the secretary of state is holding close to his vest.