This is the most important congressional moment since May 1947, when Congress supported U.S. intervention-through-aid on the anticommunist side in the Greek civil war. Congress thereby transformed containment from a theory into a policy.

Congress has now effectively killed aid for the anticommunist side in Nicaragua's civil war. Congress has forbidden even modest financial support for the military effort of a mass movement prepared to do the dying to prevent consolidation of the second Soviet satellite in this hemisphere and the first on the North American continent. The evisceration of containment is complete.

What President Reagan's aides are calling a compromise (aid restricted to nonmilitary uses) is a shattering defeat. He sought military support for a military movement and lost, utterly. On an issue he characterized -- correctly -- in the starkest moral and national security terms, his characterization was disproportionate to his effort. He did not go to the country on television. A great communicator does not deal exclusively in good news (it is time for a tax cut; America is back and standing tall). He also rallies majorities for hard decisions. Reagan has chosen to hoard his political capital -- for what? The great battle over Amtrak subsidies?

In 1947 President Truman told Congress: "I believe it must be the policy of the United States to support free people who are resisting subjugation by armed minorities or by outside pressure." Reagan's policy was -- the past tense is required -- the Truman Doctrine after 38 years of communist advance. An armed Nicaraguan minority, sustained by outside (Soviet, Cuban, East German, etc.) forces, is sovietizing Nicaragua in the way that was being done in Eastern Europe in 1947.

The Soviet Union's Sandinista clients have no more right to rule Nicaragua than Vidkun Quisling had to rule Norway. Yet the world continues to speak of Sandinista steps toward Stalinism as "failings." The Sandinistas are not somehow failing to implement democracy; those "failings" are premeditated successes.

FDR spoke of "quarantining" dictators, but an isolationist Congress resisted, until the big war arrived. Now that today's Congress has essentially spurned the contras, communist dictators on four continents will know that Congress will not permit even small inoculations, let alone quarantine.

The sum involved -- $14 million -- is 12 percent of the sum ($117 million) the U.S. government had given to the Sandinista regime by 1981. Familiar voices are saying the usual things: that the United States "drove" the Sandinistas into Soviet clutches. But in their first two years, the Sandinistas received more aid from the United States than from any other country -- five times more than the Somoza regime received in its last two years. (Someone should calculate the value in 1985 dollars of the aid France gave the American Revolution. It was, I will wager, much more than $14 million.)

During the Vietnam war, people eager to believe were encouraged by Hanoi to believe that South Vietnam was experiencing an "indigenous peasant revolt" and that the ferment in Indochina was only cosmetically communist. The Sandinistas deny their American protectors the comfort of that pretense. The Sandinistas do not deign to disguise their Stalinism at home, their "socialist solidarity" with the Soviet Union and its other clients, their "revolution without borders" against neighbors.

In 1947 Congress had fresh memories of the terrible price paid because of nonresistance to Hitler at the time of the remilitarization of the Rhineland. Today the historical memory of many members of Congress consists entirely of Vietnam and its putative lessons. But congressional management of U.S. policy toward Central America -- too little aid, too late; pursuit of the chimera of negotiated settlement with a regime that does not believe in splitting differences -- is a recipe for another Vietnam: another protracted failure.

Surely the Americans who should talk least about negotiated liberalization of the Sandinista regime are those Americans who, by trying to destroy the contras, are removing the only serious pressure on the Sandinistas.

Nicaragua's communist president, writing in The New York Times, says U.S. support for the contras is "contrary to American values." That is an odd complaint from someone who proclaims his detestation of American values, and it is an ignorant charge, given the long history of U.S. support for resistance to tyranny.

Today there are anticommunist insurgencies in Afghanistan, Angola and Cambodia. Americans opposed to the contras favor, in effect, a declaration of indifference to the only force that might enable Nicaragua to join Portugal, Spain, Turkey, Argentina and Honduras on the list of nations that have risen from tyranny to democracy.

Mikhail Gorbachev hit the ground running -- right at Pakistan, threatening reprisals if Pakistan continues to facilitate aid for the Afghan resistance. Now that Congress has spurned the contras, how long will Pakistan resist Soviet pressure? Now that Congress will not countenance support for the contras, the increasingly tinny voice of the United States will have decreased resonance in South Africa, the Philippines and other places where freedom is at issue.

It is said that an optimist is someone who believes his future is uncertain. Optimism about democracy, and not just democracy in Central America, is irrational now that, six months after a landslide reaffirmation of a president, Congress, acting in the name of fastidiousness, has removed the keystone of his foreign policy: support for democratic revolutions.