By a ratio of 50 to 1, mail to my congressional office has expressed the strongest concern I've seen about American involvement in an overseas conflict since Vietnam.

The mail is from a solid cross-section of citizens, mostly middle-class folks, many of them parents. They are the generation that were students in colleges and universities at the peak of the Vietnam War. Some of the mail is from Vietnam veterans.

The message, however, is clear, simple, direct: please, don't do it again -- don't send American boys to fight a war that isn't worth it. No more Vietnams, they say.

Meanwhile, supporters of military aid to El Salvador insist that El Salvador is not another Vietnam, and that to draw such a comparison is stretching things too far. This argument carries a long list of distinctions -- political, geographic and cultural, to prove that one just can't be compared to the other.

But Vietnam bred suspicions that linger still.

Many Americans remember when they were told the Gulf of Tonkin Resolution was the right thing at the right time, the right way to go. Vietnam or not, too much about El Salvador triggers too many memories, too much pain.

Most in the Congress, in fact, felt that Vietnam, at the outset was the correct place to "make a stand," that our Navy couldn't be shot at in the Gulf of Tonkin without our side letting North Vietnam know we weren't going to take it.

There are times when it is necessary for a country to fight a war. At the beginning of World War II, I tried to enlist as soon as I could -- in a strange bureaucratic quirk, I was told I couldn't join up because I had only one good eye, but later, the Army drafted me. I was glad and proud to go. There was a serious threat to my country. I wanted to do my part.

At the beginning of the Vietnam conflict, I was among the members of Congress who supported President Johnson. As did so many Americans at the time, I believed that what we were doing was right and just and that we could send in a few Marines, a few air strikes, and it would all be over shortly. After all, we were dealing with a country about the size of Florida. How much could it take?

But it didn't work that way. The months dragged into years and the killing and dying went on. At home, we became a nation polarized. Our cities were torn by rioting. Overseas, Americans who didn't seem to be winning anything were standing by an ally who seemed wholly indifferent to our help, our sacrifices and our commitment.

In what became the most difficult decision of my public career, I went home to Tucson in 1968, and at a Sunday Evening Forum attended by 2,400 people who had sent me to Congress, I said I thought we had made a mistake in Vietnam. I could no longer support the war. There had been too much pain, too much grief, too much horror -- with no gain.

Members of Congress, myself included, will not be misled, nor stampeded, into another tragedy. Vietnam or not, the prospect of Americans dying in battle cannot be taken lightly.

El Salvador is a tiny Central American country, smaller by about 1,200 square miles than Pima County. It has a population of 4.7 million people, was founded as a Spanish colony in the 1700s and achieved independence in 1821. For a time, El Salvador was known as the Central American Republic. It is principally an agrarian nation, and is the smallest and most densely populated country in the entire Western Hemisphere.

The origin of recent events in El Salvador reaches back to the 1972 presidential election when the army was accused of resorting to fraud to ensure the victory of Col. Arturo Armando Molina over Christian Democrat Jose Napoleon Duarte.

In 1975, the first grass-roots coalition of peasants, students and workers, known as the Popular Revolutionary Bloc, emerged. Conflict between the upper classes and government and various party, peasant, labor, church and insurgent opposition groups increased steadily after 1975.

In 1977, Gen. Charles Humerto Romero was elected president. That election was also widely dismissed as fraudulent.

By October, 1979, a group of young military officers overthrew Romero. Three civilian-military juntas have ruled the country since then. The first was composed of three colonels and three civilians and lasted until January, 1980. The second included two leaders of the Christian Democratic Party, another civilian and two colonels and lasted until December, 1980. The third, headed by Jose Napoleon Duarte, who is also the leader of the CDP, has ruled since then.

Some accounts indicate that there may be as many as five separate factions within the guerilla movement in El Salvador, each with its own program and idea of what a new government should look like. Some have avowedly Marxist sentiments.

Many of the guerillas are said to carry Soviet-made arms, smuggled into El Salvador through Nicaragua, via Cuba.

President Duarte has asked the United States for help, and we have responded with Spanish-speaking military advisers (at this writing, they number about 50) and a limited range of military equipment for the Salvadoran armed forces.

Reports of engagements between the government and guerilla forces are sketchy and sometimes difficult to follow, but there is no question that the guerillas mean to topple Duarte and establish their own government in El Salvador, if Duarte will not negotiate. Duarte and our own State Department have rejected negotiation offers so far.

President Reagan has not ruled out the use of American troops in El Salvador -- but White House aides have leaked stories to the press saying we won't use American troops in this conflict.

And our own policy of not allowing American advisers to carry rifles is itself "under review." I have gone on record opposed to issuing rifles to our advisers. An armed military man becomes a legitimate target, and one shot means escalation. Placing any U.S. troops in any combat situation brings the War Powers Act into play, which would require the President to report to Congress the full extent of our involvement. Our people now in El Salvador are allowed to carry sidearms, but arming them beyond that is not good sense. We would only be inviting a much wider conflict -- and that is precisely what we are working to avoid.

Yes, there is cause for concern about what is happening in El Salvador. Nicaragua today stands in the hands of the Sandinistas, who boast of close political ties to Cuba. Cuba stands firmly entrenched in the Soviet bloc. El Salvador is too close to home not to be concerned.

Not far north of El Salvador are the oil fields of Mexico, in which the United States has a definite interest. They stand as an inviting target for terrorists. Given the proximity of El Salvador to Mexico, it is no wonder that Mexican President Lopez Portillo has announced that Mexico is moving ahead quickly with development of an elite combat unit whose specific mission will be to protect those oil fields.

Since the adoption of the Monroe Doctrine in the early 1800s, the United States has intervened militarily a number of times in Central America and the Caribbean. We had Marines in Nicaragua almost without interruption between 1911 and 1933. In part because of our involvement, no foreign powers held influence in Central America or the Caribbean until the late 1950s, when Fidel Castro came to power in Cuba.

The era of "gunboat diplomacy," however, is over. We no longer can restore order in these countries by simply sending in a gunship or a few Marines. The times have changed. In each of the Central American countries there are fierce nationalistic movements that are both popular and resentful of foreign intervention, including American intervention.

The thought of El Salvador falling into the hands of a Marxist-oriented government is a disturbing one. It would represent not just one more country, but another in a line of countries too close to our borders, coming under the influence of a foreign power that bears us no glad tidings.

But we are not facing the same kind of situation that prompted President Kennedy to stare down Nikita Khrushchev over the Cuban Missile Crisis in 1962. What Nicaragua has in the way of ground forces, while more than they need for self-defense, are nothing close to the threat posed by the offensive ICBMs that were being based in Cuba in the 1960s.

We have a serious threat in a highly unstable and highly volatile part of the world, our own backyard. What then, to do?

Second, we must insist that El Salvador take firm steps to improve its record with regard to human rights. That must come in exchange for continued American support and aid.

Third, we should offer a proposal for the creation of a Latin American peacekeeping force, composed of troops from member nations of the Organization of American States.

Fourth, Congress should move quickly on President Reagan's plan for a new assistance program for Latin America. While I may have differing views on some parts of the President's proposal, I believe the intent is sound, has merit and deserves support.

Susan Kaufman Purcell, a member of the policy planning staff at the State Department in both the Carter and Reagan Administrations, has some good thoughts about what our approach to Central America should be. Writing in the Los Angeles Times, she said:
 

Latin America does not belong to the United States, nor to the Soviet Union. It belongs to the proud and fiercely nationalistic people who inhabit all her nations, and it is to those people that the job of securing long-term stability and peace in the region must fall.