NARRATION: After World War II, fears of spreading communism took Americas Cold War battle to every corner of the globe.

ARCHIVAL (1-1-47):PRESIDENT HARRY TRUMAN: It must be the policy of the United States to support free peoples who are resisting attempted subjugation. If we falter in our leadership, we may endanger the peace of the world.

NARRATION: U.S. economic interests long drove American foreign policy in Latin America. But the success of the Cuban revolution in 1959 focused attention on the dangers of the Soviet Unions ideological expansion so close to home.

ARCHIVAL (ASSOCIATED PRESS, 1962):NEWS REEL: In less than four years Fidel Castro, who came to power on a wave of personal popularity, has allowed himself to become dominated by Russia. Her support now constitutes a threat to western security.

NARRATION: In response, the U.S. supported coups against leftist governments in Brazil, Ecuador and Chile, and even sent U.S. troops to the Dominican Republic. Then, in 1979, Nicaraguas U.S.-backed dictatorship fell, sending new alarm bells off in Washington.

ARCHIVAL (1980S):NEWS REPORT: Nicaragua has become the first Soviet foothold on the continent of the Americas. A military buildup unprecedented for Central America aided by nearly 2000 military and security advisers form Cuba.

RAYMOND BONNER (FORMER CENTRAL AMERICAN CORRESPONDENT, THE NEW YORK TIMES): American foreign policy makers feared that it was creeping communism, that it was going to be Nicaragua, El Salvador, Guatemala, all the way up to the soft underbelly of Kansas.

NARRATION: U.S. officials turned their attention to El Salvador, where military repression of popular dissent had fueled a growing leftist insurgency. The tiny country soon became Americas line in the sand.

ARCHIVAL (ABC, 2-1-82):FRANK REYNOLDS: It was said here today the decisive battle for Central America is underway in El Salvador.

ARCHIVAL (12-3-82):PRESIDENT RONALD REAGAN: If we do not act promptly and decisively in defense of freedom, new Cubas will arise from the ruins of todays conflicts.

ARCHIVAL:JEANE KIRKPATRICK: Were not talking about an effort that is focused on a single country, Salvador. We are talking about an effort that affects an area of enormous geopolitical importance to us, the United States.

ROBERT WHITE (1926-2015, FORMER U.S. AMBASSADOR TO EL SALVADOR): If I recall correctly, Secretary of State Haig went to President Reagan and said, Mr. President, this is one you can win, quote, unquote.

NARRATION: Military and economic aid poured into the country, as did American military advisors. And Reagan threatened to go further.

ARCHIVAL (CBS, 2-3-82):NEWS REPORT: The White House today refused to rule out the eventual use of American combat troops to help prevent the overthrow of the government in El Salvador.

NARRATION: But the strategy emboldened El Salvadors right-wing government, which had already shown itself adept at political violence.

ARCHIVAL (ABC, 2-1-82):BARRIE DUNSMORE: For U.S. policymakers the case of El Salvador fits the classic definition of diplomacy; choosing between the undesirable and the unacceptable. The question remains how far is the U.S. prepared to go to prevent the unacceptable?

TERRY KARL (PROFESSOR EMERITA, LATIN AMERICAN STUDIES, STANFORD UNIVERSITY): President Reagan gave almost a green light to fighting this war any way the Salvadoran military wanted to fight it. The way they wanted to fight it was a strategy of massacres. And that strategy meant the chief victims in El Salvador in this civil war were always civilians, always unarmed people.

NARRATION: In the end, more than 75,000 Salvadorans were killed, and there was no quick victory.

ROBERT WHITE: Ten years later, they were still fighting and our main contribution was to destroy El Salvador over the next ten years. A whole generation was wiped out. The productive capacity of El Salvador was terribly damaged, and it was simply a case where our reaction lacked all proportionality. We tried to defeat an authentic revolutionary movement, and it proved impossible even in a postage-stamp country the size of El Salvador.

NARRATION: And El Salvador was far from alone.

SERGIO BITAR (FORMER CHILEAN MINISTER AND SENATOR): For Latin Americans, always we have had the problems that we had the government of the United States looking to us and seeing as a devil any social change.

NARRATION: American foreign policy had supported autocratic rulers throughout Latin America.

ARCHIVAL (NBC, 2-20-81):ROGER MUDD: The Reagan administration extended the official hand of friendship to another military or authoritarian government today, this time to the government of Chile.

SERGIO BITAR: The U.S. was responsible for the evolution of Latin America into the hands of dictators and civil wars. It was a desert of dictators, the whole region in the South and then the whole civil wars in Central America.

NARRATION: Americas complex legacy in the region continues to play out today.

NELSON RAUDA (SALVADORAN JOURNALIST, EL FARO): Its hard to realize, but the U.S. Government is still dealing with the consequences of what the U.S. Government in the 80s did. Of all the uncivilization, their policies cost in Central America and Guatemala and Honduras, in El Salvador, in Panama even, in Nicaragua, that failed foreign policy, will affect the U.S. for decades.

RAYMOND BONNER: Part one of the consequences is the crisis we see on the border today with immigration.

TERRY KARL: If you pursue endless war as a government policy, you will get immigrants. You will get refugees.

NARRATION: Looking back, Americas actions often had the opposite effect of what they were supposed to achieve.

ROBERT WHITE: National security had become the justification for actions that actually jeopardized our national security and did not reinforce it.

RAYMOND BONNER: I mean its an old clich you know, Those who forget history are doomed to repeat it, but we need to look at it and say be careful about who you support, who you get in bed with. We need to learn our lessons.