Jack Valenti argues in his op-ed piece [Nov. 29] that to understand the new secret tapes of President Lyndon B. Johnson's private conversations on Vietnam, contained in my recently published book, "Reaching for Glory," you must know this about him: that LBJ did not seek a World War II-style unconditional-surrender victory in Vietnam, that his aim was instead to break the back of the enemy and force him to negotiate.

The problem is that if this was his intention, he did not confide it to the Americans he was sending into harm's way in Vietnam. Indeed, within a week of his first large escalation of ground combat forces in 1965, Johnson told an audience, "America wins the wars that she undertakes. Make no mistake about that." Later he exhorted soldiers to "nail the coonskin to the wall" and told them, "We know you're going to get the job done."

More to the point, as the tapes reveal, Johnson was privately tormented as early as February 1965 by the suspicion that in Vietnam he would fail even to achieve the limited goal Valenti insists was his aim. He tells Defense Secretary Robert McNamara that he can't imagine anything "as bad as losing" and doesn't see "any way of winning." A few months later, he says of the Viet Cong adversary, "I don't believe they're ever going to quit."

Johnson's dread in 1965 that his Vietnam war would end in catastrophe was why he sank into the depression that his wife, Lady Bird, describes in her taped diary transcripts. She says LBJ told her: "I can't get out, I can't finish it with what I've got and I don't know what the hell to do." She has him telling her that regarding Vietnam, he felt as if he were in a crashing airplane and "I do not have a parachute." These are not the words of a man confidently expecting that his escalation in Vietnam will lead to a North Vietnamese cave-in and negotiation.

Johnson believed in the domino theory, as Valenti writes. Most Americans did in 1965. Valenti is correct in saying that had Johnson pulled out of Vietnam in 1965, he would have had to defend himself against the charge of seeming soft on communism.

So we must refrain from chastising LBJ for failing to see what most of us see 36 years later: that defending the unpopular and corrupt regime in Saigon was not essential to winning the Cold War -- and that the cost the Vietnam War exacted from us in blood, treasure and national self-confidence was much too exorbitant for anything we gained.

What is chilling, however, is how brilliantly Johnson understood in 1965 -- not '68 but '65 -- the tragedy that was about to unfold. On the secret tapes, he privately predicts that the Senate and the American people will abandon his war and the nation will not be able to sustain such a commitment based on such a small and shrinking reservoir of support. He predicts America will lose in Vietnam, that the Viet Cong will fight on and on. He does not disagree with the hauntingly accurate prediction of his old Senate mentor, Richard Russell, that the Vietnam War could take a decade, kill 50,000 Americans and end in our first defeat.

My point is this: Why didn't this well-intentioned man share these private doubts with the American people in 1965 and give us a full sense of how costly he believed it would be to keep the commitment to South Vietnam? Presidents should always level with Americans -- especially when they are asking us to enter a major war.

Johnson could have gone on television and told us: "As your president, I believe we have to wage a major war in Vietnam. You should know that it could take many years, kill many Americans and we still might not win." Had he confided in us his fears about the smashup that lay ahead, I am not so sure that people would have been likely to demand that he thrust us into a large-scale war in Vietnam.

Johnson would have been aided in this had he asked for help from Sen. Russell, a Georgia hawk known as "Mr. Defense" who was head of the Armed Services Committee. In private, Russell told LBJ repeatedly that Vietnam was not our war. In the summer of 1965, he confided to Johnson his horror that Vietnam's leader, Gen. Nguyen Cao Ky, was saying he would let Americans do the fighting in Vietnam while his own troops hung back, engaging in pacification. Russell told LBJ, "If they're going to try to fight that kind of war, I'm in favor of getting out of there."

Russell and LBJ were both so brilliantly right and prescient -- in private. Had they shared their qualms and unvarnished assessments with the American people at the time, our democratic system might have worked the way the Founders wanted it to and spared us the horrors of Vietnam.

Michael Beschloss is an author and presidential historian.