WHEN FRANK CARLUCCI becomes secretary of defense, he will take to the job a decades-long record of excellence in the national security arena. The same is true of Lt. Gen. Colin Powell, the new national security adviser. Unfortunately, such expertise at the top levels of our national-security apparatus is not the rule. As a consequence, we confront an extended crisis of competence in the making of our national-security policy.

There are many reasons for policy failures -- bad ideas, bad values, bad politics, bad judgment, bad luck. Sometimes presidents ignore sound advice. But a prevalent cause of U.S. national-security mistakes in recent years is simply lack of expertise on the part of our policymakers. America cannot afford to rely on well-meaning but inexperienced corporate managers, investment bankers, lawyers, politicians, former top officials from domestic agencies and inexperienced academics to manage national-security policy any more than we would choose such people to run our armed forces.

The problem did not start with the current administration. The Carter presidency at the outset was seized with a raw popu-lism, a disregard for all that had gone before. One remembers the misguided commitment -- later retracted -- to withdraw U.S. troops from South Korea, the maladroit attempt to pressure West Germany into stopping civil nuclear sales to Brazil, the abrupt about-face on neutron bomb deployment days after securing European agreement. The damage to America's world role from episodes like these continued into President Reagan's first term, not least because of the Reagan administration's early ideologically-based refusal to hire most people who had been influential at a senior level on foreign or defense policy for Presidents Nixon or Ford.

In Lebanon, for example, the administration defied advice from the experts and committed the United States to a futile intervention that ultimately culminated in the death of 241 servicemen. At the Reykjavik summit with Gorbachev last October, the administration stumbled into a confused exploration of non-nuclear utopia and perfect defenses. The costs were considerable: mistrust among our closest foreign friends and a weakened capacity for effective U.S. leadership.

As the Tower Commission demonstrated in the case of the Iran-Contra affair, these flaws are not principally caused by the basic structure of national-security decisionmaking machinery. The problem is usually with the people, not the process. Indeed, in many of these cases from the past decade, the process was deliberately misused by its managers to produce a sort of reverse Darwinism: thoughtful and expert participants -- from professional foreign service and intelligence officers to Cabinet secretaries -- were cut out, leaving an inexperienced, if deeply committed, circle of policymakers.

Incompetence is especially costly now when the Soviet Union, despite its profound internal weaknesses, possesses a dynamic leadership with unprecedented capability for the shrewd pursuit of its foreign policy goals. In nuclear arms control, Gorbachev has skillfully coopted credit from us for the 'zero option' for intermediate-range nuclear forces in an agreement that has worried many of our closest allies in Europe. In conventional arms control, a 1986 Moscow-devised call for new negotiations obscured ongoing negotiations on force reductions in Central Europe, and aggravated western alliance divisions.

In the Mideast, the Persian Gulf, Afghanistan, East Asia and the UN, Gorbachev has coupled new initiatives with hints of flexibility to try to focus world attention on the Soviet rather than the American agenda.

Behind this array of initiatives is an impressive Soviet team. Its members are not larger than life. They make mistakes. But they are deeply experienced. Aleksandr Yakoklev, a Politburo member and key advisor to Gorbachev on foreign policy and international propaganda, went to Columbia University as an exchange student and then steadily worked his way up through the ranks of the Communist Party's propaganda department. He balanced this experience with more than ten years' service as Soviet Ambassador to Canada, supervision of a government foreign policy think-tank, and authorship of several books on the United States. (Imagine the value of a U.S. cabinet officer involved in national security questions, who had studied in the Soviet Union, spent a decade living next door to the USSR, and spoke fluent Russian).

Anatoly Dobrynin, Party Secretary held the post of Ambassador to the United States for 25 years, attending every U.S.-Soviet summit meeting during six administrations. His right-hand man, Georgiy Korniyenko served as Dobrynin's deputy in Washington in the early 1960's and then spent the next 20 years in the Foreign Ministry, always focusing on East-West, U.S.-Soviet and arms control issues. The Foreign Ministry official with direct responsibility for arms control, Yuliy Vorontsov, has spent 25 of his 35 years as a career diplomat alternately in Moscow or in the United States as well as serving as Soviet Ambassador to India and France. And there are a bunch more folks like these in Gorbachev's Moscow.

Presidents too know how to find expertise when they believe it is necessary. Federal Reserve Board Chairman Alan Greenspan, for example, earned a reputation for analytical brilliance as an economic consultant, won praise as chairman of President Ford's Council of Economic Advisers, and forged a difficult compromise solution as head of the bipartisan National Commission on Social Security Reform. His predecessors were similarly skilled in the fine points of monetary policy and central bank interventions. Yet where is the same insistence that those who take charge of our foreign and defense policy and their subordinants enter office with a sure grasp of, say, nuclear deterrence or the Arab-Israeli dispute?

It is wrong to assert that, at high levels of responsibility for national security, the necessary skills can or should be acquired through on-the-job training. As Henry Kissinger pointed out in his memoirs, "It is all illusion to believe that leaders gain in profundity while they gain experience . . . . The convictions that leaders have formed before reaching high office are the intellectual capital they will consume as long they continue in office."

Similarly misguided is the commonly held belief that policymaking consists of a few grand decisions, taken at critical moments, that then set the course for the future. This concept of occasional steering is no more true for international affairs than it is for driving a car. (And the ditches on the sides of the national security road are deep). Proper guidance requires a multitude of tiny corrections, an incremental process of continous negotiation inside an administration, with Congress, and with foreign countries. Moreover, the essence of successful national security decisionmaking lies in defining the situation before it becomes a crisis. Like brain surgery or coaching in the NBA, it is not a job for beginners. But beginners we often get.

Our problems should not be written off as another inevitable adjunct of the American democratic system. Many administrations including this one have benefited from the services of persons who combined outstanding ability and experience, people like George Marshall, Dean Acheson, Robert Lovett, Charles Bohlen, George Ball, Brent Scowcroft, Zbigniew Brzezinski, Harold Brown, Alexander Haig, Carlucci, Vernon Walters, Paul Nitze, and Max Kampelman. Though these individuals came from a variety of backgrounds, all had years of government experience with national security problems before they ascended to higher positions of public trust in Washington. (Henry Kissinger is an incandescent and accomplished exception to this pattern; we are unlikely to beat the odds a second time soon). And none of these distinguished individuals were or are ideological zealots, a litmus test few competent people pass.

It is useful to recall that, when recruiting his NSC subordinates in 1969, Kissinger rejected half a dozen suggested political appointees. He insisted on "no other criterion than quality." The resulting extraodrinary staff included Haig, Lawrence Eagleburger, Helmut Sonnenfeldt, William Hyland, Winston Lord and Harold Saunders, and was the best ever.

When recent presidents used the expertise at their disposal they have achieved notable foreign policy successes -- the Carter administration's Camp David accords between Egypt and Israel, for example,and the Reagan administration's successful 1981-83 effort to deploy Pershing II and cruise missiles in Europe. Though by no means absolute, there have thus been demonstrable correlations, buttressing the intuitively obvious connections between expertise and success -- and amateurism and failure.

National security expertise is not the exclusive province of those who share a particular political, ideological, or strategic perspective. But, whatever his beliefs, if a person is sufficiently talented and does not succumb entirely to the arrogance of power, he will make fewer errors in his second year on the job than in his first, and so on. By using gifted people who have already learned from directly relevant experience, including their own mistakes, we can avoid repeating these frequently damaging, sometimes clownish learning cycles every four years or even more often. (The Reagan administration has had six national security advisers in seven years).

Personalities -- and their interplay -- are also crucial. As Alexander the Great lay dying, his generals asked him to name who would rule his empire. He is said to have replied, in a last whisper, "To the strongest." This bequest was a prescription for chaos 2300 years ago. It is no better guide for bureaucratic politics within the Executive Branch today. From the well-publicized bickering between Kissinger and Defense Secretary James Schlesinger to the strife between Defense Secretary Caspar Weinberger and Secretary of State George Shultz, recent presidents have had little success in bringing together a smoothly functioning foreign and defense policy team.

Presidents could avoid much of this bickering if they spent some time studying how well their prospective appointees have previously worked with others or whether their national security views meshed.Instead we have witnessed divisive and incapacitating struggles such as that between Cyrus Vance and Zbigniew Brzezinski over U.S.-Soviet relations and the response to the Iranian crisis during the Carter years and endless disputes over strategic arms control during the Reagan administration. If President-elect Reagan at the end of 1980 had sent Haig, Weinberger, Richard Allen, Michael Deaver, Edwin Meese, William Clark, Donald Regan, and James Baker on a long fishing trip into the Canadian north woods to discover how they would get along, one wonders how many and which ones would have returned in one piece. National-security experts like Carlucci and Powell will not solve all of our nation's foreign affairs problems. But they will perform far better than the fumbling amateurs and ideologues administrations often foolishly choose in their stead.

Robert Blackwill was U.S. ambassador to the conventional-force negotiations in Vienna from 1985 to 1987. Now on leave from the Foreign Service, he is teaching at Harvard's Kennedy School of Government.