UNITED STATES POLICY towards Latin America moves in repetitive cycles that might be amusing were not their consequences tragic. Periodically, an American administration discovers that opposition to a friendly dictator is reaching flash point and begins to distance itself from him. The irony, of course, is that the dictator, typically, was boosted to power by the United States at an earlier point in the cycle.

Currently, the State Department is attempting to arrange a graceful exit for Anastasio Somoza, whose family has run Nicaragua for over four decades. The state of affairs between Somoza and his people was made clear late last summer when they rose in revolt and he sent his planes to bomb and strafe them. While the United States now favors Somoza's departure, officials are concerned about a "power vacuum" when he goes. (A similar concern surrounds another U.S.-supported dictator lately fallen on difficult days -- the Shah of Iran.)

It is the reappearance of this particular kind of foreign policy crisis that makes Piero Gleijeses' excellent new book on the Dominican Republic so timely. Years of research and hundreds of hours of interviews with the participants gird Gleijeses' analysis of the aftermath of the United States having soured on another Caribbean dictator, Rafael Trujillo, in 1960. Withdrawal of U.S. support for Trujillo was hailed by the Dominicans. But the prestige won thereby was soon squandered by subsequent U.S. meddling in Dominican affairs. It all climaxed in 1965 when a popular revolt for democracy and constitutionalism broke out, only to be crushed by an invasion of U.S. Marines.

Gleijeses writes with passion and stinging criticism about that American intervention, but never without careful documentation. This definitive work should be read and pondered for what it reveals about American foreign policy, both past and present.

Like the Somozas in Nicaragua, Trujillo had come to power courtesy of an army created, trained, and equipped by the United States, left behind after a Marine Corps occupation in the 1920s. When he was assassinated in 1961, a power struggle began among his family, hangers-on, military factions, and the Dominican upper class. The mass of Dominican citizens were silent witnesses to that struggle but their chance came in 1962 when they overwhelmingly elected Juan Bosch, a popular political leader who had spent 25 years in exile under Trujillo.

Seven months after his inauguration, Bosch was overthrown by a military coup. He had given the Dominican Republic the most honest government in its history. Now, corruption began again on the grand scale. A few military officers, convinced the country needed a return to its constitution, began to plot a countercoup. Meanwhile, the United States, a principal actor in the political maneuvering since Trujillo's demise, had thrown its wholehearted support to the conservative government installed by the military to replace Bosch -- a government with no popular support.

Gleijeses' superb description of the progress of the countercoup makes clear how complex were the motives of the officers joining. A few were committed to the constitutionalist ideal. Most hedged their bets, hoping only to wind up on the winning side. When the coup began on April 24, 1965, many of those who had promised support held back. The rebels captured Santo Domingo, the capital, but the officers they'd counted on to swing key bases behind them vacillated. Initiative swung to their enemies, who still controlled more men, all the tanks and planes in the country, and the navy. A merciless bombardment of the city began, softening it for the final blow, a tank-led sweep by a powerful infantry force across the Duarte Bridge. The coup's leaders threw in the towel, sought asylum in embassies. Only a couple remained, resigned to a pointless but honorable death among the leaderless soldiers and civilians being massacred at the Duarte Bridge. But at the bridge they found a population in arms, bottling up the army's tanks in narrow streets, resisting every foct of the advance. The attack stalled. At dusk on April 27, the army fled back across the bridge. For the first time in their history, the Dominican people had won. Their freedom lasted barely 24 hours.

The U.S. embassy had approved the naval and air bombardment of the city and the tank attack "even though it could mean more bloodshed" because "it is the only way to forestall a leftist takeover," as the embassy cabled. But when the attack failed, when the panicky Dominican military began to disintegrate, the embassy called for the Marines. Lyndon Johnson, who had represented the U.S. at Bosch's inauguration, gave the orders that crushed the revolt seeking to restore him to office.

Clearly, the fear of communism played a major role in U.S. actions in 1965. It was a fear out of proportion to the situation since, as Gleijeses painstakingly demonstrates, the Dominican left was weak and faction-ridden throughout the period. President Carter has said American policy makers are no longer dominated by an "inordinate fear of communism." Even if that is so, there are other patterns in the Dominican case which still characterize U.S. policy: ignorance about the mood of the mass of people, be they Dominicans, Nicaraguans, or Iranians; preference for dealing with the upper class, no matter how isolated they may be from their own people; the conviction that the military, no matter how criminal and how hated, is the basis of stability and must be kept intact; the assumption that after years of supporting a repressive regime, the U.S. will be accepted as an impartial mediator; and finally, the mechanical refusal to countenance popular leaders, like Bosch, or the Sandinistas in Nicaragua, whose cardinal sin is not their politics but their refusal to take American advice.

Gleijeses shows how, in 1965, all these factors combined to produce a shameful episode in the United States' relations with its neighbors. His own sympathies are clearly with the people who courageously fought an army and its tanks for freedom at the Duarte Bridge. The pity is that in such stirring scenes, U.S. officials so often see only a threat.