Lyndon Johnson was eloquent, back in 1965, about the dread consequences which would befall the world if the United States failed to frustrate the legions of communism in Vietnam.
Henry Kissinger's eloquence was equal in fervor (though phrased in more scholarly fashion) in 1976 when he tried to persuade the Congress and American public opinion that Soviet intervention in Angola had to be frustrated.
President Reagan is just as fervent in these days when he tries to push and prod a reluctant Congress into supporting a broad campaign of anticommunist action in Central America.
In view of the fact that observers in El Salvador think the rebels seem to be gaining the upper hand and will probably win unless the US sends its own troops into combat (which Mr. Reagan has said he will not do), it is worth looking back over how many dominoes did fall after LBJ's crusade in Vietnam failed and after Congress refused to fund Dr. Kissinger's efforts to rescue Angola from Moscow.
Back in 1965 when President Johnson was sending half a million American soldiers to Vietnam there was a widespread and seriously held belief among many of the top figures in government in Washington that failure to fight in Vietnam would mean all Southeast Asia going communist.
In the more lurid versions of the domino theory communism would then leap the Indian Ocean to Africa, sweep across Africa, and then spread to South America.
Well, the US did fight in Vietnam. It spent 47,079 American lives. Public opinion turned against the war. The Americans left. Ten years after Mr. Johnson sent his armies into Vietnam the communists from the north swept down over the south and all of Vietnam became a communist country.
Their victory encompassed all of what previously had been French Indochina - Vietnam, Cambodia, and Laos. But that is where it all stopped. No more dominoes fell.
Today Vietnam's neighbors are among the more successful and prosperous of the ''Newly Industrializing Countries'' - called NICs. Thailand and Singapore do particularly well. Indonesia, Malaysia, and the Philippines are less prosperous but coming along.
All of them are protected from Vietnamese imperialism by China's differences with Moscow. Vietnam is a client of Moscow. China supports a small anti-Vietnam rebel force in Cambodia. China has attacked Vietnam once, and shows occasional signs of doing it again. There is constant friction along the China-Vietnam frontier.
Rivalry between China and the Soviet Union has neutralized the domino theory for Southeast Asia.
Dr. Kissinger said that failure to prevent Soviet intervention in Angola would be a ''catastrophe.'' He wanted both covert and overt US aid to the ''other side'' in Angola. The Soviets had picked one of three rival political movements in Angola. Mr. Kissinger wanted to back the other two.
Congress did not agree. First the Senate by 54 to 22, then the House by 323 to 99, voted to forbid covert aid for both Angola and Mozambique. President Ford called the votes in Congress ''a deep tragedy for all countries whose security depends on the United States.''
So, since 1976, governments which call themselves Marxist have existed in both Angola and Mozambique. There are 200 Soviet and 18,000 Cuban troops in Angola; 300 Soviet and 750 Cuban troops in Mozambique.
But Angola's trade is mostly with the West. The US is the biggest single customer taking 38 percent of Angola's exports, mostly in crude oil pumped into Gulf Oil Corporation tankers under protection of Cuban troops. American corporations doing business in Angola favor US recognition. Washington says recognition can come only when Cuban and Soviet troops leave. Angola says Cuban and Soviet troops are necessary for protection against rebels in the south supported from South Africa. Informal negotiations continue between Angola and Washington.
Mozambique's trade is also almost entirely with the West. The US is also the largest customer.
Communism has not spread out from Angola or Mozambique. The Soviets have not obtained important advantage from their investment in those countries.
There has been no ''catastrophe'' for the West. In six years no neighboring dominoes have fallen. Countries which depend on the US for their security have not said they feel less secure.