Thunder at Foggy Bottom! Secretary of State Al Haig was threatening to quit. "I just hope he won't self-destruct," one aide recalls thinking. "He's already had a heart attack."

Barely into its third month, the administration stumbled into a confrontation: President Ronald Reagan appointed Vice President George Bush head of the task force to deal with foreign crises. Haig hadn't been told in advance, and, according to State Department sources, his high dudgeon had aides shuttling in one after another seeking a compromise, to no avail.

Enter William Clark, the slow-walking, slow-talking deputy secretary of state, the son and grandson of California ranch hands and Reagan's longtime confidant. Clark listened to Haig, and then he called the president, his sometime partner in long horseback rides through the California countryside.

Soon enough, in that mysteriously genial way that is Clark's forte, the peace was made and the OK Corral of Washington turf wars was, for a while, A-OK once again.

"The president seems to have a certain special trust in Bill Clark," says Helene von Damm, the president's assistant who was originally hired by Clark, then Gov. Reagan's chief of staff, to be his secretary. Von Damm says that when the Reagan presidential campaign was at its lowest point -- just before the firing of campaign manager John Sears -- Reagan called Clark, then a judge on the California Supreme Court, to come over to his ranch. The two of them talked for seven hours about what needed to be done. "In his hours of need, Reagan goes back to Bill Clark," von Damm says.

Last week Clark's talent for trouble-soothing and trust landed him in the national security adviser's slot, following the political Gethsemane of Richard Allen.

According to a high White House source, Reagan's three principal aides -- James Baker, Edwin Meese, Michael Deaver -- brief the president at 8 each morning. At 9:30, Clark meets with the president. Depending on Clark's choice, he might bring an expert in a given area, for instance Caspar Weinberger or one of the Reagan troika. The Reagan-Clark meetings are unstructured, similar to their meetings in Sacramento during Reagan's governorship.

Clark is not just a Reagan loyalist, but a man in the Reagan mold. They are both big-time ranchers who started out poor and Democratic. He is a charter member of the close-knit group that gathered around Reagan in Sacramento. As Gov. Reagan's chief of staff, Clark worked with an upstart budget-cutter named Caspar Weinberger and hired two young fellows, Edwin Meese and Michael Deaver. Clark's most recent friends are State Department professionals who once thought him a threat and a joke.

When the president announced that he had picked Clark for the State Department's No. 2 post, many Foreign Service liberals concluded that Clark would be the man to crack the whip over them, and Haig, according to one close friend, marked Clark off as a Reagan crony sent to spy on him. Many had cause to gloat over the disaster of Clark's Senate confirmation hearing -- his not knowing the name of the prime minister of Zimbabwe, etc. Foreign Relations Committee Chairman Charles Percy, a Republican, declared: "Never again can we accept a man who professes to have no knowledge in the area for which he has been nominated."

But that was last spring. Sen. Joseph Biden Jr. (D-Del.), who asked those embarrassing questions, now welcomes Clark's promotion. He says that Clark is "fully capable of being a facilitator of access to the president" -- the original role for the national security adviser.

At State, Clark has sought out experts for a privately tutored crash course in foreign policy. One State Department professional praises him for "not rubbing in his conservative philosophy like other Reagan appointees have done." Several other bureaucrats pay him a special tribute: He gets things done.

Last August, Stan Anderson was scheduled to leave for Nairobi as the president's special representative to head the U.S. delegation to the United Nations' energy conference. But his letter of accreditation from the White House was missing. Anderson's frantic staffers called Clark for help. Clark's call reached Anderson in a limousine on his way to the airport. "Go ahead," Anderson remembers Clark saying, "I'll take care of your appointment." And he did.

Clark's elevation to the post Henry Kissinger made famous received much approval from foreign-policy experts, including Kissinger, apparently relieved that the usual feud between the State Department and the National Security Council will cool off.

'A Touch of the Daredevil'

But who is the man behind the affability?

"He has the judicial temperament of being able to work with different people," says von Damm. "He can get angry -- but nothing excessive. When things bother him, he doesn't communicate. He broods. He works things out in himself." His hobby is collecting and restoring buggies and other horse-drawn agricultural implements.

Edwin Meese's wife, Ursula, recalls having been with her children on Clark's six-seater Cessna, which Clark was piloting. "The plane was not safe," she says, "but I felt safe about Bill. He has a sureness about himself."

Clark had several small crashes in commuting from Los Angeles to his ranch near the tiny town of Shandon, in San Luis Obispo County. On one occasion, with all his five children aboard, the plane got caught in crosswinds and turned over. Miraculously, no one was hurt. But Joan Clark talked her husband out of future flights. "I didn't veto his flying," she now says, "I worked in more subtle ways. He came to see that it wasn't so smart to have a plane. But I didn't ground him." "There is the touch of the daredevil in Bill," says Ursula Meese.

"He is a master of the art of the mini-memo," says Joan Clark, referring to his innovation of condensing for Gov. Reagan reams of reports into five salient points.

Joan Clark is trim, petite, well-spoken. She describes herself as content being a 19th-century wife to a workaholic husband. "We do find time to be together as a family," she says. "But work has to get done first." With the White House job, she says, she sees even less of her husband.

"I have no profile," he tells a reporter. "But if you want to see me . . . well, come on over. Just talk to my scheduler."

Having answered his own phone, he puts through his scheduler. She is casual to the point of giggles -- more California than Foggy Bottom. She says Bill Clark just doesn't have the ego that goes with the job.

He is a big man with regular features; a young 50, with a full head of dark hair. He looks you in the eye when he shakes your hand. He takes his jacket off and tells his guest to do the same.

"I hope you clean up my syntax," he says. "I am just rolling it around."

"Just rolling it around" is a favorite expression of his. It means that he is just tossing words in the air; he is ready to revise his views. And he is open to other ideas.

He doesn't radiate brilliance or self-confidence. He seems to let you in on his feeling that everything will be okay.

If a little leaner in the jaw and around the waist, Clark could pass for one of Reagan's pals from the days when Hollywood fought World War II. Clark has a rolling gait. He chews on the stem of his eyeglasses.

When discussing foreign policy, his speech slows down; his caution is that of a good student seeking to avoid mistakes.

California Connection

He says that the Reagan administration's foreign policy has "a more European approach -- many short, solid steps in many directions." He singles out Namibian independence, expected by the end of 1982, as an example of the administration's success in breaking an impasse. He says that what helped was a new approach to South Africa which reflects "our Californian upbringing not to criticize friends and relatives in public, but to work it out in private."

"Reagan and my husband are both Western men," says Joan Clark. "They love the outdoors. They are at ease with themselves -- nothing neurotic about them. No identity crises. Their feelings are genuine, and that's why people take to them."

Joan Brauner Clark, 50, is a refugee from Czechoslovakia. Her family, originally Austrian, first went to East Germany and then fled to West Berlin, one by one.

She met Bill Clark when he was stationed in West Germany with the U.S. Army. She acknowledges they went to Switzerland to get married, on the sly, because in 1955 a counterintelligence officer was not permitted to marry a foreigner.

In Washington, the Clarks live in a small apartment furnished sparsely with functional modern furniture. The tiny balcony looks on another part of the building. It is the kind of temporary place rented by a Foreign Service officer awaiting assignment abroad.

Nine months after the Clarks moved in, framed photographs of their five children are still on the living room floor -- Joan Clark says that she is still hoping that she can hang the pictures with her husband. The room's focal point is a contemporary tapestry of St. Francis of Assisi. The Clarks are devout, conservative Roman Catholics. They go to church every Sunday and prefer the Latin mass.

Their apartment building is not luxurious. Its advantage is that it is a three-minute walk from the Kennedy Center, which they visit at least once a week. They both love classical music; Mozart is their common favorite. Joan plays the piano.

Their typical week calls for five evenings out -- dinners and meetings with diplomats, administration officials. All business. Joan Clark says she is never bored at Washington dinner parties and considers her social life "an excellent education in foreign affairs." During the day she studies Spanish at the Foreign Service Institute.

Reagan and Clark first met in 1966, after Clark, then a prominent lawyer in the small town of Oxnard, became county chairman for Reagan's gubernatorial campaign. When Reagan won, he surprised Clark by inviting him to be his chief of staff. According to Hugh Flournoy, then state comptroller, Clark's innovation was "opening up the governor's cabinet to consultations." Flournoy sums up Clark as "a patient man who doesn't come with any predetermined conclusions."

Clark helped to prove that the Reagan philosophy -- until then a series of dinner speeches on 3-by-5 cards delivered to like-minded audiences -- --could work in the nation's most populous state. Clark was not only present at the creation; he was the creator's right hand.

But why did Clark quit after a year and a half? "He just wasn't that interested in politics," says Joan. But, she says, Reagan talked him out of returning to private law practice and named him judge -- first to the county superior court, then the appeals court, and finally the California Supreme Court.

"Judge Clark was very conservative," says a colleague. "He reflected Reagan's judicial philosophy. He was for strict law enforcement. He looked for the plain meaning, rather than read into the law other meanings. But he was very fair and listened to all sides."

What the President Wants

The one issue that makes Clark's stomach rumble is fiscal irresponsibility. He broke with the family tradition of voting Democratic after he concluded that LBJ's Great Society spent more money than it earned. He decided that Reagan was his man after he heard Reagan speak at a dinner for Barry Goldwater's presidential campaign.

From the days of the transition team, President Reagan had Clark on his mind. According to Clark, after he let it be known that he did not want to be considered to head the CIA, or serve as secretary of agriculture or as attorney general, Reagan dispatched Edwin Meese to San Francisco to talk Clark into taking the State Department's No. 2 post. Meese's argument was that the president really, really needed him. Clark said he couldn't make up his mind until he met with Haig. According to Joan Clark, her husband wouldn't have taken the job if Haig had been reluctant to accept him. Asked why he took the State job after declining the others, Joan Clark says, "When the president asks you to work for him, how can you keep saying no?"

His salary dropped from $72,855 to $50,112 when he accepted President Reagan's offer to change his black robes for the striped suit of diplomacy. "Oh, it's not a matter of material gain," he says. "We have gone into our assets to live here."

The Clarks will stay in Washington as long as the president wishes them to. Though Clark ruled himself out for the Supreme Court, he says he will take "almost any job" the president wants him to do. "Somebody has to do the job," Joan Clark explains.

The Clarks are determined to return home -- their ranch of 900 acres, halfway between Los Angeles and San Francisco. They will raise cattle and barley, tend their orchard. They will ride horses and be with their children, aged from 17 to 25. (The oldest is in charge of the ranch now.) They made their down payment on the ranch in 1964 and are proud to own it free and clear.

In 1981, he managed to get back home only once, for three days. The president has suggested that the two of them keep horses hitched to a tree at Vandenberg Air Force base. But, Clark says, there is no tree at that air base.

"At the beginning, he used to ask if the pressure never stops," says one of his assistants at State. "Like all outsiders, he was surprised by the speed things are done here. But he caught on quick. He now knows that he is on call 24 hours a day and it's one crisis after another. You haven't even learned all the names and factors in one crisis, and there is another crisis to deal with. He has learned to pace himself. He can handle several urgent matters one after the other, he can move from one crisis to another. He doesn't get bothered."

State Department partisans of human rights credit Clark with rescuing that issue from the wastebasket. After the Senate rejected Ernest Lefever's nomination to head the human rights bureau, Clark negotiated the appointment of Elliot Abrams, who, unlike Lefever, is a vigorous advocate of human rights.

Several U.S. ambassadors thank Clark for their appointments. An impatient Haig, according to State Department sources, kept pressing a more-than-usually-slow Reagan White House, but it was Clark who got the signatures.

Clark's humiliation at the Senate confirmation hearing was not his first. After his nomination to the California Supreme Court, the press discovered that he had dropped out of college and later from law school -- before he went to night school and passed the bar.

He denies having hard feelings about those "setbacks" -- as he calls them. "It was fair game," he says. "It's what made it all the more worthwhile."

Those present at the Senate hearing remember him as shaken. It's hard to believe that he has such a strong ego as not to care about public humiliation or that he has no ego to be humiliated. What he has is a great need to show that even in the face of adversity he is easygoing. All the way. No matter what.

For Clark, the middleman, mediation is the message; a friendlier world is the goal. The emblem is that easygoing smile when the pressure is on; it is a copy of the Reagan smile. It is as soothing as jellybeans. Or an old World War II movie with the good guys winning.