331. Memorandum From the President’s Special Assistant (Rostow) to Secretary of Defense Clifford1


As I told you the other day, I think that your press conference hit precisely the right tone in relating the current lull to the enemy’s expected third offensive.2

I was troubled, however, by some of your remarks on the bombing.

I would agree that before March 31st the enemy had decided to increase substantially his infiltration. Furthermore, there is certainly no evidence—and I have no reason to argue—that the restriction of the bombing has had any effect whatsoever on his decision to engage in this massive infiltration effort.

However, I cannot agree that

  • —the restriction on the bombing has had no effect on the number of infiltrees arriving in SVN;
  • —the enemy will move the men and materiel they choose to; and
  • —if their losses go up in the process of moving, then apparently they just move more men and supplies.

In my view, we simply do not have enough information to make a net judgment of the impact of the bombing restriction on the number of infiltrees.

On the plus side, we do not know that

  • —the restricted bombing campaign is much less costly to us in terms of aircraft and crew losses;
  • —we have been killing many more trucks and a larger percentage of the trucks moving south.

On the negative side, however, we know that

  • —greater numbers of trucks and people than ever before are getting through;
  • —the elapsed time for movement of men and supplies has probably been substantially decreased because they enjoy a free ride down to 19 degrees. (A decrease in transit time, of say 30 to 50 percent, decreases the enemy’s pipeline requirement by a corresponding amount.)

We simply do not know:

  • —to what extent the greater efficiency in killing trucks results from greater concentration of effort or from improved techniques of detection and attack;
  • —whether attacking trucks north as well as south of 19 degrees would have the net result of more or less supplies getting to the south;3
  • —how the level and rate of flow of men and supplies would be affected by attacks on targets other than trucks north of 19 degrees.3

The major uncertainty in any of our evaluations of the bombing is that we have no way of knowing what the enemy would really like to do. Hence, we have no way of evaluating the restraints which the bombing places on the fulfillment of his desires.

I understand—and have lived for many years now in amiable disagreement with—the argument which states that:

  • —enemy requirements in SVN are limited (although I personally believe the intelligence experts have consistently underestimated the magnitude of these requirements);4
  • —enemy inputs to meet these requirements are relatively small in comparison with their total requirements and in any event are easily supplied by outside sources without cost to NVN;5
  • —therefore, it is an easy matter for the enemy to budget for whatever level of effort he desires in the south.

There is a fundamental fallacy in this notion that the enemy has necessarily achieved what he desires.

In any real war, the net thrust in the field results from a balancing of all the factors rather than from the subordination of all else to a single absolute priority. This rule holds for every war of which I know, in my own experience or from history. In government—even totalitarian government—there is never an absolute priority. In this case the enemy’s activity must be considered against a background of the total constraints upon him. Hanoi has to budget not just for its activities in SVN but for its total war effort: feeding, clothing and housing their people; air defense; repair; recruitment and training.

For example, I do not doubt for a moment that the enemy would have wished to mount an even larger offensive at Tet. In their current efforts to get ready for a third crack at us, I do not doubt that they would want to put in as much as they could against us to make this effort decisive.

Therefore, I must conclude that there were effective constraints on the enemy’s level of effort at Tet just as there are constraints which affect his third offensive.

The major constraint acting against him is, of course, our forces and allied forces in the field in the south. One of the other constraints has been and remains our bombing of the north.

You will find that arguments which begin with the notion that the enemy is putting in all he “chooses to” shift—at a certain point—to: in any case, “bombing is not decisive.” Of course it is not decisive. But our action in SVN has not been decisive yet either. No one constraint is, in itself, decisive. Our task is to build all those constraints to the point where he decides to accept as his best realistic option what we mean by an honorable peace.

The bombing is, then, simply one of the constraints operating against the enemy. Any reduction of our bombing effort enables him to increase the weight of his effort against us in the field.

One way to put the question is this: If we stop bombing, would Hanoi cancel the shipment of supplies to the south or send fewer men?

The answer obviously is no. With the battle in its present intense and perhaps critical stage, Hanoi is trying to get the maximum possible impact within limits set by all its constraints.

In any case, Clark, that is my reaction to: “they will move the men and material that they choose to”. Life and war are just not like that.

  1. Source: Library of Congress, Manuscript Division, Nitze Papers, Vietnam War, Courses of Action—Post Paris Talks, 1963, 1967–1968, n.d. Secret.
  2. Clifford’s August 15 speech contained, in addition to the specifics mentioned in this memorandum, a mention that bombing would end if the DRV informed the United States “that they have reduced the level of combat, and that that constitutes a de-escalatory step.” See The New York Times, August 16, 1968.
  3. A notation in Nitze’s hand reads: “within limits we do.”
  4. A notation in Nitze’s hand reads: “within limits we do.”
  5. A notation in Nitze’s hand reads: “30 tons-60 tons-600 tons.”
  6. A notation in Nitze’s hand reads: “why in disagreement.”