Those who have been watching the current television series on the history of the Vietnam war will have noticed how wide was the gap between the assumptions of the original American intervention and the realities of the results.
In the beginning, President Eisenhower approved substantial US assistance to France on the theory that, if the French were driven out of Vietnam, communism would spread out from Vietnam to the surrounding Asian countries. He and his secretary of state, John Foster Dulles, were particularly eloquent about the danger to Western trading and commercial interests. The raw materials of Indochina would be lost to the West.
The French were driven out and the United States took up the burden of trying to keep communism out of the southern half of Vietnam, and it failed. The war did spread into Laos and Cambodia, but largely on US initiative. Communism went with the war into those two neighboring countries.
But communism did not spread beyond the borders of what had been Indochina. The principal neighbors - Thailand, Singapore, and Malaysia - are today among the prosperous and highly capitalist Asian NICs (newly industrialized countries) which are giving lively competition in light industry to Japan, the US, and Western Europe. The only commercial interests to suffer are those hurt by competition from the countries that did not go communist.
The dominoes did not fall. Something quite different happened. All of Indochina is now under Vietnamese control. Vietnam has become a major bone of contention between Moscow and Peking. The Chinese have invaded Vietnam punitively once. They keep up a threat of a second invasion. They support isolated rebel groups, particularly in Kampuchea, which are still in the field resisting Vietnamese forces supported by Moscow.
One condition the Chinese currently make for a resumption of easier Peking-Moscow relations is withdrawal of Soviet support for Vietnam.
What the US wanted most out of US intervention in Vietnam was the prevention of the spread of ''monolithic communism'' from Indochina to other nearby countries.
US intervention did not achieve the purpose. But the withdrawal of US forces from Vietnam did. The practical effect of US intervention in Vietnam was to delay what Washington most wanted. It gets that result now from rivalry between Moscow and Peking.
The Marines are now taking casualties almost every day in Lebanon. They are there for the official purpose of trying to help set up an independent Lebanon. But the effect of their presence at the present moment is delaying the process by which an independent Lebanon might come into existence.
It is difficult to know how to use military force to achieve a specific political purpose. This is an instance where use of force is a disservice to the original purpose.
The problem is simple. There can be an independent Lebanon if first the various elements that make up the population can agree among themselves on a fair division of power in a new government. If Christian Maronites, Druzes, Sunni, Shiite Muslims, and Palestinians could all agree on a constitution and form of government and on fair division of the powers of government, the foundation would exist for an independent Lebanon.
The present trouble arises from the fact that the US Marines were sent in to try to sustain and encourage a regime that was unacceptable to a majority of the people and groupings.
The dominant element in the present government is the Gemayel faction. It does not even have the support of all the Maronite Christian factions. It has enjoyed Israeli subsidies in the past and is still relatively friendly with the Israelis.
The fact of past Gemayel association with Israel automatically makes it unacceptable to most Muslims, to some Maronite Christians, and to all those in association with neighboring Syria. Syria could not accept a Lebanese government friendly to Israel. The Gemayel faction had proved its friendliness to Israel by accepting an agreement with Israel.
Thus the deployment of the Marines has the unintentional effect of delaying that sorting out of the relations among the Lebanese factions which must precede the formation of the kind of government that could unite Lebanon and might obtain both a Syrian and Israeli withdrawal from Lebanese territory.
Withdrawal of the Marines would probably mean more civil war in Lebanon. But that may be a necessary part of the sorting out process. The one thing the US Marines cannot do is make the Gemayel regime acceptable to the majority of Lebanese.