Gaddis Smith, Larned Professor of History at Yale, specializes in the history of American foreign policy in the 20th century.

Whatever happened to the Monroe Doctrine? For more than a century, the Doctrine was the proud, explicit symbol of the unilateral assertion of American power and interest in this hemisphere, and especially in Central America and the Caribbean. In 1984, the United States is asserting that power and interest with renewed intensity, but the magic phrase, which once ranked with the Declaration of Independence and the Constitution in the pantheon of American reverence, has been dropped from official discourse. This raises interesting questions: Why and when did the words disappear? And what has happened to the substantive policies that the words once signified?

President James Monroe's original message to Congress in 1823 had three parts. First, the United States considered the Western Hemisphere closed to any future European colonization. Second, and most important, the United States would regard any attempt by European nations ''to extend their system to any portion of this hemisphere as dangerous to our peace and safety.'' And third, the United States would abstain from involvement in European political affairs. The particular threats against which Monroe inveighed - further Russian colonization on the Pacific coast and European monarchical attacks on the newly independent Latin American republics - soon dissolved. Monroe's message was forgotten for a generation. In 1833, for example, when the British reoccupied the Falkland Islands after the departure of a small Argentine garrison, the United States did not protest. But in the 1840's, President James K. Polk, intent on limiting British claims in the Oregon Territory, brought the Doctrine back to life. By the end of the 19th century, it was a full-blown shibboleth. Under the Monroe Doctrine, said Secretary of State Richard Olney in 1895, ''the United States is practically sovereign on this continent, and its fiat is law upon the subjects to which it confines its interposition.'' This blustering affirmation quickly became known as ''the Olney corollary'' - the first of many expansions and interpretations of the original Doctrine. The particular occasion was American insistence that Great Britain submit to arbitration a boundary dispute between its colony of Guiana and Venezuela.

The next corollary bears the name of President Theodore Roosevelt. In 1904, the United States, having driven Spain from Cuba and Puerto Rico, and having begun construction of the Panama Canal, was uneasy over events in the Dominican Republic. It appeared that political chaos and financial irresponsibility might tempt European powers to intervene, and in the process acquire a naval base that would threaten the Panama Canal. President Roosevelt decided the United States would have to intervene first, in order to force the Dominican Government to behave - thus making intervention unnecessary. The general principle of the Roosevelt corollary was stated by the President, as follows:

''Chronic wrongdoing, or an impotence which results in a general loosening of the ties of civilized society, may in America, as elsewhere, ultimately require intervention by some civilized nation, and in the Western Hemisphere the adherence of the United States to the Monroe Doctrine may force the United States, however reluctantly, in flagrant cases of such wrongdoing or impotence, to the exercise of an international police power.''

The Roosevelt corollary converted the Monroe Doctrine from a stated attitude toward Europe to a justification for United States action against Latin American nations. Under the umbrella of this corollary, the United States proceeded during the next three decades to control the government and finances of the Dominican Republic, Haiti and most of Central America. Cuba had been under American control since 1898, and it remained so. Sometimes American troops were stationed in the countries under control; sometimes they were unnecessary.

President Woodrow Wilson expanded American intervention under the Monroe Doctrine. He did emphasize an American mission to nurture democratic ideals rather than the necessity of protecting American security, but the results for the countries being controlled were the same no matter what the rhetorical justification.

Wilson's most significant contribution to the Monroe Doctrine accompanied the American entry into World War I. The President's efforts to maintain at least nominal American neutrality in the European war - which would have been consistent with a major proviso of the original proclamation - had failed by the beginning of 1917. As he prepared to lead the nation into war, Wilson sought a goal higher than merely punishing Germany for its misuse of the submarine. He also needed to explain the nation's abandonment of one part of the Doctrine. His solution was idealistic and ingenious:

''I am proposing, as it were, that the nations should with one accord adopt the doctrine of President Monroe as the doctrine of the world: that no nation should seek to extend its polity over any other nation or people, but that every people should be left free to determine its own polity, its own way of development, unhindered, unthreatened, unafraid, the little along with the great and powerful.''

The United States entered

the war. Germany lost. And in 1919, President Wilson at the Paris Peace Conference supervised the drafting of the covenant of the League of Nations. The League's basic purpose was to provide a collective guarantee of political independence and territorial integrity to all nations, a global Monroe Doctrine according to the vision of Woodrow Wilson. But skeptical United States senators said League of Nations involvement in the Americas would violate the Doctrine. Wilson, under pressure, persuaded his European colleagues at the peace conference to add Article 21. It stated: ''Nothing in this Covenant shall be deemed to affect the validity of international engagements, such as treaties of arbitration or regional understandings like the Monroe Doctrine, for securing the maintenance of peace.''

Article 21 failed to assuage American patriotic fears, because the Monroe Doctrine was not an international engagement or regional understanding. It was a unilateral statement of national interest and hegemony in the Americas. The Senate Foreign Relations Committee bluntly rejected Article 21 as inadequate. According to one of the conditions proposed for American entry into the League of Nations, the committee declared that the Doctrine ''is to be interpreted by the United States alone and is hereby declared to be wholly outside the jurisdiction of said league of nations.''

Wilson in 1920 lost his fight for American membership in the League of Nations, and the next decade saw the Monroe Doctrine revered as never before. On its 100th anniversary in 1923, an estimated 10 million schoolchildren sat through a reading and discussion of the Doctrine in class. New Yorkers heard it on prime time over the pioneer radio station WEAF. A full-page advertisement in The New York Times quoted Mary Baker Eddy: ''I believe strictly in the Monroe Doctrine, in our Constitution and in the laws of God.'' During the same decade the Senate, while approving American participation in the World Court at The Hague, expressed formal reservations over the supposed conflict between an international juridical body and America's absolute freedom of action under the Doctrine. The Senate also explained in 1928 that American adherence to the Kellogg-Briand Pact renouncing war as an instrument of national policy did not apply to action under the Monroe Doctrine.

Events of the 1930's had a profound impact on the meaning and use of the Doctrine. The successive administrations of Presidents Herbert Hoover and Franklin D. Roosevelt realized that the phrase was a public-relations liability in Latin America. The words made patriotic hearts beat faster north of the Rio Grande, but to the south they meant Yankee imperialism. Accordingly, the Hoover Administration in 1930 formally declared that nothing in the Doctrine justified United States intervention in the internal affairs of Latin American nations, thereby renouncing the Theodore Roosevelt corollary. Franklin Roosevelt withdrew the last American troops from Central America and the Caribbean (the Canal Zone excepted), ended the formal protectorate over Cuba and spoke in terms of a ''good neighbor'' policy rather than the Monroe Doctrine.

A second factor was the aggressive, expansionist behavior of Japan in Asia and Nazi Germany in Europe. Japanese publicists and officials gleefully proclaimed the Monroe Doctrine an excellent precedent for Japanese imperial aspirations in Asia. How could the United States possibly object? The comparison left Cordell Hull, Roosevelt's Secretary of State, almost apoplectic with anger.

In 1940, after Nazi Germany defeated the Netherlands and France, Washington fretted over the possibility that German-controlled puppet governments might assume power in Dutch and French colonies in this hemisphere. The United States Government invoked the Monroe Doctrine and declared it would act to prevent such a transfer. Adolf Hitler's answer was that he would be delighted to respect the Monroe Doctrine if the United States would recognize a similar doctrine for Europe and would abide by Monroe's original injunction to stay out of European affairs. Cordell Hull again sputtered with indignation, but henceforth the Roosevelt Administration tried whenever possible to secure a collective definition of hemisphere security from all the American republics, in preference to unilateral invocation of the Monroe Doctrine. At the same time, creative government geographers officially accepted the view that Greenland and even Iceland were within the Western Hemisphere and thus under the protection of the Monroe Doctrine.

Nazi Germany was responsible for another significant new dimension to American thought and action under the Doctrine. Before Hitler came to power, European threats were relatively straightforward: a possible naval base, a new or expanded colony, the establishment of a puppet monarch (Emperor Maximilian of Mexico, set up by the French in the 1860's). But in the 1930's and 1940's, the United States saw the Nazi threat primarily in terms of subversion - ''fifth columns'' within targeted countries spreading propaganda, infiltrating the governments, controlling communications. ''The United States will, therefore, have to develop new techniques for preventing the introduction of alien systems under modern conditions,'' wrote Nicholas Spykman, a widely read authority on national security, in 1941.

New techniques were developed and applied against German influence. They included the emplacement of covert American agents; the gathering and evaluation of secret intelligence; military training and the supply of weapons; subsidies for friendly politicians and newspapers, and economic warfare. The German threat disappeared with Hitler, only to be replaced almost instantly by fear of subversive Soviet influence. The techniques learned against Nazi Germany were polished, expanded and applied to the new situation of cold war, applied not only to Latin America but wherever in the world a Soviet challenge was perceived.

President Harry S. Truman gave public voice to the new policy in 1947. The specific context was a request to Congress for support of Greece and Turkey against Soviet pressure. The press immediately called the new departure the ''Truman Doctrine,'' a deliberate echo in tribute to Monroe's proclamation. Later Presidents - Eisenhower, Nixon, Carter - would also have ''doctrines'' named after them, but only Truman's would rival the original in recognition and acceptance.

The cold war brought forth what could be called the Kennan corollary of 1950. Early in that year, George F. Kennan, the influential diplomat regarded as the principal author of the policy of ''containment'' against the Soviet Union, made a tour of Latin America. He was not pleased by what he found: selfishness, inefficiency, an obscene gap between the rich and poor. The region seemed ominously ripe for Communist subversion, and Latin American leaders, especially those professing liberal values, appeared to lack the capacity to resist. Kennan believed that the Monroe Doctrine and the national security to which it referred were at stake. The main work of resisting Communist penetration, said Kennan in a long report to Secretary of State Dean Acheson, ''must be done for the most part by natives of the particular country concerned.'' Since all Latin American countries did not have a strong tradition of democratic government, this meant that the United States could not be squeamish about the methods employed. The heart of his argument, the Kennan corollary to the Monroe Doctrine, deserves to be quoted at length:

''We cannot be too dogmatic about the methods by which local Communists can be dealt with. . . . Where the concepts and traditions of popular government are too weak to absorb successfully the intensity of Communist attack, then we must concede that harsh governmental measures of repression may be the only answer; that these measures may have to proceed from regimes whose origins and methods would not stand the test of American concepts of democratic procedure; and that such regimes and such methods may be preferable alternatives, and indeed the only alternatives, to further Communist successes.''

George Kennan in 1984 may not be entirely happy with this formulation of 1950. But the ideas he expressed 34 years ago run like a dark thread through more than a third of a century of American policy. For example, in 1954, the United States, acting covertly through the Central Intelligence Agency, applied the Kennan corollary with a vengeance by arranging the overthrow of a duly elected but leftist government in Guatemala. Secretary of State John Foster Dulles proclaimed a victory over Communist subversion throughout the hemisphere. He added that ''this intrusion of Soviet despotism was, of course, a direct challenge to our Monroe Doctrine, the first and most fundamental of our foreign policies.'' This was the last occasion on which the Doctrine was prominently invoked by a high American official.

The Kennan ideas are behind Lyndon Johnson's 1965 intervention in the Dominican Republic. They are present in a remark made by Henry Kissinger in 1970, while trying to prevent the election of Salvador Allende in Chile: ''I don't see why we need to stand by and watch a country go Com- munist due to the irresponsibility of its own people.'' (In 1973, three years after Allende was elected president, he was murdered during a military coup supported by the United States.) They are related to Ronald Reagan's and Jeane Kirkpatrick's thesis that the United States should not criticize authoritarian governments of the right, lest they collapse and give way to totalitarian governments of the left. And they are implicit in justification for a military solution to the turmoil in El Salvador and for aid to the ''contras'' seeking to overthrow the Sandinista Government of Nicaragua.

The last 25 years in the history of the Monroe Doctrine, since Fidel Castro came to power in Cuba in 1959, have witnessed avoidance of the phrase itself, but vigorous and expanding application of some of the Doctrine's ideas and corollaries. Nikita Khrushchev struck a sensitive nerve in July 1960 when he attacked the Monroe Doctrine as a mere pretext for American domination of Latin America. The State Department issued an indignant rebuttal, reminiscent of Cordell Hull replying to the Japanese or Germans.

Two years later, Khrushchev started to install nuclear missiles in Cuba and thereby issued the most serious of all challenges to American security and the ideas of the Monroe Doctrine. But President John F. Kennedy deliberately avoided invoking the phrase. He and his closest advisers knew that Latin Americans equated the Monroe Doctrine with intervention. Kennedy wanted the United States to be perceived in terms of another symbol, the Alliance for Progress. When a Justice Department memorandum suggested the United States could claim special legal rights in the hemisphere under the Monroe Doctrine, President Kennedy was disdainful of using such a rubbery set of ideas for a legal argument. ''The Monroe Doctrine,'' he said, ''what the hell is that?'' The press repeatedly tried to draw Kennedy into discussion of the Doctrine, but he refused. Kennedy did refer to the Doctrine in the luncheon address never delivered in Dallas on the day he was assassinated in 1963. But characteristically he was arguing for power, not mere words, as the source of security: ''It was not the Monroe Doctrine that kept all Europe away from this hemisphere - it was the strength of the British fleet and the width of the Atlantic Ocean.''

The missile crisis ended with Soviet agreement to withdraw the missiles in return for an American pledge not to invade Cuba. This outcome reduced a very real threat of nuclear war, but it hardly represented a triumphant vindication of the Monroe Doctrine. Indeed, it was tacit recognition that Castro's Cuba was now under the protection of the Soviet Union. Critics on the right went on the attack. Edward V. Rickenbacker, World War I fighter ace and chairman of the board of Eastern Airlines, joined William F. Buckley Jr. in forming a Committee for the Monroe Doctrine to protest the Kennedy-Khrushchev agreement. Barry Goldwater and Richard Nixon advocated redefining and reinvoking the Doctrine. The New York State Conservative Party passed a resolution praising the Doctrine and calling for the ouster of the Communist regime in Cuba by whatever means necessary. The flurry of discussion of the Doctrine provoked by the Soviet presence in Cuba died away. In 1968, Soviet troops crushed a liberal regime in Czechoslovakia, and Premier Leonid Brezhnev justified the deed by saying that the Soviet Union had a right to intervene in the internal affairs of fraternal nations in order to defend the gains of Socialism. The fact that this policy instantly became known in the West as the ''Brezhnev Doctrine'' indicated that a comparative allusion to the Monroe Doctrine was still recognizable. But the negative connotation of the Brezhnev Doctrine, so completely hostile to the ideal of self-determination, placed an additional inhibition on the explicit invocation by Americans of the Monroe Doctrine. Direct mention virtually disappeared. (The New York Times Index records only two incidental references from 1968 through 1978.)

The year 1979 brought an intensified sense to Washington that the United States was threatened in this hemisphere. The Sandinistas won power over the reactionary regime of Anastasio Somoza in Nicaragua and quickly showed themselves unwilling to be obedient followers of the United States. Marxists staged a successful coup in Grenada. Left-wing insurgency mounted against the military regime in El Salvador. The United States Government revived old policies. Even the phrase ''Monroe Doctrine'' began to be used - although not by Administration spokesmen. Jimmy Carter wanted to be remembered as the President who believed in partnership with Latin America. He was proud of ending a remnant of American colonialism by returning the Canal Zone to Panama. A revival of the phrase ''Monroe Doctrine'' would have damaged that image. For example, in 1979, during the flap over the alleged Soviet combat brigade in Cuba, the House of Representatives passed an amendment authorizing President Carter to restrict exports to any nation he found in violation of the Monroe Doctrine. In 1981, Richard Nixon invoked the Doctrine in declaring: ''We cannot allow the Soviet Union to get a further foothold in Latin America. Cuba and Nicaragua is enough.'' And in 1982, both houses of Congress passed a resolution in favor of stopping Marxism-Leninism in the Western Hemisphere by ''whatever means may be necessary . . . including use of arms.'' A spokesman for the sponsor of the resolution described it as a reinstitution of the Monroe Doctrine.

President Reagan and members of his Administration have, like their predecessors since John Foster Dulles in 1954, avoided using the words ''Monroe Doctrine.'' Whether they are being careful about offending Latin American sensibilities or are merely unaware of a historical symbol is not clear. But the connection between the concepts of the Doctrine and the Administration's deeds is clear. The intervention in Grenada in October 1983 marked the return of the Theodore Roosevelt corollary. The attempt in the spring of 1984 to exclude issues relating to Central America from the jurisdiction of the World Court - specifically, the refusal to be judged on the matter of mines planted under C.I.A. supervision in the harbors of Nicaragua - recalls the opposition of the 1920's to the World Court of that day. The rejection by the present Administration of the Carter Administration's emphasis on human rights and the return of tolerance for ''harsh governmental measures of repression'' used against the left is precisely the Kennan corollary of 1950.

The year 1984 saw the appearance of a new corollary containing an ironic reversal of one aspect of the original Doctrine. James Monroe opposed European intervention in this hemisphere because it threatened American security directly. His companion injunction against American involvement outside the hemisphere was abandoned by Woodrow Wilson, revived briefly by isolationists between the two world wars, but permanently put aside after 1941. In 1984, however, the old injunction was turned on its head. The report of the commission on Central America appointed by President Reagan and headed by Henry Kissinger declared that the threat of a Marxist-Leninist advance was dangerous not only in itself, but because it would limit the capacity of the United States to intervene around the world. The Kissinger corollary, as it should be called, argued that if it became necessary for the United States to mount a direct military defense of its southern border:

''We would either have to assume a permanently increased defense burden, or see our capacity to defend distant trouble spots reduced, and as a result have to reduce important commitments elsewhere in the world. From the standpoint of the Soviet Union, it would be a major strategic coup to impose on the United States the burden of defending our southern approaches, thereby stripping us of the compensating advantage that offsets the burden of our transoceanic lines of communication.''

One aspect of the Monroe Doctrine has not changed in a century and a half. It has always been a unilateral, and at times even a blatant, expression of American national interest and power. Since Guatemala in 1954, American leaders have realized that the phrase could not be used without incurring resentment in Latin America or inviting other great powers to claim similar doctrines in their spheres. That is the fundamental explanation of the Doctrine's descent into anonymity.

Despite an occasional call from the political right to ''remember the Monroe Doctrine,'' it is unlikely that 10 million schoolchildren will ever again have to endure a reading of the old message or that a high official will again call the Doctrine ''the most fundamental of our foreign policies.'' But the Doctrine's concepts will remain alive, although unnamed, as long as the American Government and people believe it is right and necessary for the United States to act unilaterally in this hemisphere, to intervene in the affairs of other nations or to define alone what standards of international law the United States will or will not follow.