DEAR STUDENT LEADERS:

I have received and read carefully your thoughtful letter to the President about our policy in Vietnam.

Your interest and your concern are shared by most thinking Americans. No one desires more strongly to bring an early and honorable conclusion to the conflict in Vietnam than those who are working day and night, both here and in Vietnam, to achieve that end.

The questions you have raised are among those that have been asked and discussed repeatedly in the councils of your Government. If some of these matters continue, as you say, to agitate the academic community, it is certainly not because answers have not been provided. It is more, I think, because the answers to great and complex questions can never fully satisfy all the people in a free and questioning society.

Nevertheless, I am glad to have the chance to address myself to the four specific questions about which you and others felt doubt or concern.

First, you asked if America's vital interests are sufficiently threatened in Vietnam to necessitate the growing commitment there.

There is no shadow of doubt in my mind that our vital interests are deeply involved in Vietnam and in Southeast Asia.

We are involved because the nation's word has been given that we would be involved. On February 1, 1955, by a vote of 82 to 1 the United States Senate passed the Southeast Asia Collective Defense Treaty. That Treaty stated that aggression by means of armed attack in the treaty area would endanger our own peace and safety, and, in that event, "we would act to meet the common danger." There is no question that an expanding armed attack by North Vietnam on South Vietnam has been under way in recent years; and six nations, with vital interests in the peace and security of the region, have joined South Vietnam in defense against that armed attack.

Behind the words and the commitment of the Treaty lies the lesson learned in the tragic half century since the First World War. After that war our country withdrew from effective world responsibility. When aggressors challenged the peace in Manchuria, Ethiopia, and then Central Europe during the 1930's, the world community did not act to prevent their success. The result was a Second World War -- which could have been prevented.

That is why the Charter of the United Nations begins with these words: "We the peoples of the United Nations, determined to have succeeding generations from the scourge of war, which twice in our lifetime has brought sorrow to mankind..." And the Charter goes on to state these objectives: "to establish conditions under which justice, and respect for the obligations arising from treaties and other sources of international law can be maintained ... and to unite our strength to maintain international peace and security..."

This was also the experience President Truman had in mind when--at a period when the United Nations was incapable of protecting Greece and Turkey from aggression -- he said: "We shall not realize our objectives unless we are willing to help free peoples to maintain their free institutions and their national integrity against aggressive movements that seek to impose upon them totalitarian regimes."

These are the memories which have inspired the four postwar American Presidents as they dealt with aggressive pressures and thrusts rfom Berlin to Korea, from the Caribbean to Vietnam.

In short, we are involved in Vietnam because we know from painful experience that the minimum condition for order on our planet is that aggression must not be permitted to succeed. For when it does succeed, the consequence is not peace, it is the further expansion of aggression.

And those who have borne responsibility in our country since 1945 have not for one moment forgotten that a third world war would be a nuclear war.

But the hard and important fact is that in the postwar world external aggression has not been permitted to develop its momentum into general war.