66. Airgram From the Department of State to the Embassy in Vietnam1


Subject: Interdiction. For Nolting from Harriman. The use of air power in counterinsurgency operations in Viet-Nam has been subject to continuing study and refinement. The Country Team, and particularly the military members of the Country Team, are to be commended for their constant efforts to increase the effectiveness of our air advantage in Viet Nam.

However, we must never forget that this is a political war and since more than a year has now passed since we began our expanded assistance to Viet-Nam, we feel that we must now undertake a careful evaluation of the future use of both American and Vietnamese air power against the Viet Cong.

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There appears to be no doubt of the great value of the increased mobility which transport planes and helicopters have conferred on the RVNAF. Relief by air power of units, posts, and hamlets under attack has proved very important. Reconnaissance by air is also most valuable. In the case of close air support for Government-initiated offensive operations, the picture is not so clear, however, and further study seems in order. But we are particularly struck by the difficulties of assessment with regard to interdiction missions.

In an effort to clarify the value of air interdiction missions and place them in proper perspective, we have drawn up the following balance sheet. We are aware that our information is incomplete. The great difficulty here is that, basically, any evaluation of the usefulness of air interdiction tends to become an evaluation of the temper of the Vietnamese people. The difficulties of assessment do not make it any less important, however. We therefore request that the Country Team consider the following statement of the problem, give us their comments, and wherever possible, provide us with more complete information.


We understand that U.S. piloted combat fixed-wing aircraft now fly about 1,000 sorties monthly. Of these, about 530 are in direct support of ground actions. Over 300 of the remainder are interdiction missions. These, as we understand it, are independent air strikes against ground targets believed to be Viet Cong positions or bases.

Targets for interdiction missions are often inhabited. Given the Viet Cong dependence upon the people, it is believed likely that many Viet Cong bases and installations include numbers of persons who are not hard core Communists, who are less than wholehearted supporters of the Viet Cong, or who may even be basically anti-Viet Cong.

Joint US-Vietnamese procedures for checking targets and controlling aircraft to insure that they hit the right target have been very carefully worked out and refined. They are believed to be basically sound. The intelligence on which targeting is based, however, comes from Vietnamese sources which are often difficult to evaluate. To the degree that this intelligence is faulty or imprecise, the likelihood of injuring or killing civilians is increased.

We have in fact received scattered reports of civilians being injured and killed by interdiction missions. Considering the difficulty in separating out Viet Cong personnel from the general population, plus the sources of our intelligence, this is probably to be expected. The problem, then, revolves around the reactions of the Vietnamese population to these injuries and deaths. We must seek to weigh popular Vietnamese reactions to the civilian casualties which are inflicted by air power against the value of Viet Cong casualties so inflicted.

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Another, somewhat separate, but equally important factor in the problem is the American presence. We have been at great pains to put strict limits on our role in this war, not only for domestic reasons, but also because the mere appearance of either American control or direct participation in the war gives substance to the main theme of Communist propaganda, i.e. that Diem is an American puppet, that this is a neo-colonial war, and that all patriotic Vietnamese must fight for their independence against the United States.

In examining this problem the following specific factors must be considered, they are set forth as arguments, of varying degrees of validity, pro and con.


Interdiction missions appear to have contributed substantially to the progress already registered against the Viet Cong. Intelligence reports and POWs indicate that one of the most serious problems which the Viet Cong confront is how to react to air power. Air attacks are credited with inflicting heavy casualties on the VC. They no longer feel safe in their base areas and are under constant psychological pressure as a result. Their growing logistic problems stem at least in part from the destruction of supplies by air raids.
Evidence of popular resentment resulting from interdiction missions is slim. We do not know that injuries or deaths of civilians have generated any substantial degree of hatred or resentment against either the GVN or the United States.
We do not know how many innocents have been injured or killed. Given the care with which proposed targets are examined, the number could be quite small.
Targeting procedures have been continually refined and intelligence is improving. Fewer and fewer civilians should therefore be involved in interdiction strikes. The Strategic Hamlet program also helps. As that program progresses, the Viet Cong should be progressively separated from the people, thus reducing the chances of air strikes resulting in civilian casualties.
In this war we work under a number of limitations, most notably, presumed enemy safe havens and secure bases across international boundaries. We should not deny ourselves the full use of those advantages which we enjoy. A principal advantage is our monopoly of air power.
While there has been rising concern in the United States about the American combat role in Viet-Nam, both in terms of interdiction missions and close air support, international opinion seems to have been affected very little. Aside from the Communist bloc, our efforts to help the Vietnamese defend themselves appear to have been accepted without much difficulty. Within Viet-Nam, there is little or no evidence [Page 176] that the American role in the use of air power against the Viet Cong is resented or that it has helped advance the Communist propaganda line.
The Vietnamese are not yet capable of conducting the war from the air without our help. Our air efforts in Viet-Nam, including interdiction missions, are an important part of training the Vietnamese to defend themselves and to take over the war effort.



The U.S. objective in Viet-Nam is to assist the Government to reestablish predominant control over its national territory. To do this the GVN must win the support of its citizens. While destroying Viet Cong targets makes life immediately more difficult for the VC, the lasting result may be to create resentment among people who are living in the target areas or who have friends and relatives there. We cannot assume that the people in the target areas have chosen to be governed by the VC. There are probably very few in Viet-Nam who are such hardened and committed Communists that they cannot be won back to support of the Government.

This is a political war. To regard any territory as enemy or any villages as VC is a dangerous oversimplification.


We do not know with any certainty the reactions of the Vietnamese rural population to interdiction missions. It is known, however, that the VC are able to recruit with little or no difficulty in many areas. The growth in VC strength in spite of very heavy casualties in the course of the past year is dramatic evidence of this. It is not unreasonable to suspect that an important factor in the ease of VC recruitment is popular resentment generated by interdiction strikes.

It could be argued that each time an inhabited VC target is hit, serious political antagonism is created in the vicinity, and that these antagonisms would be deepened in localities subjected to repeated air strikes. [Page 177] The French experience suggests that both propositions are true. Since these targets can rarely be reached on foot, it would be quite difficult to assuage resentments so generated by sending in civic action teams to help with reconstruction. It seems unlikely that GVN broadcasts, or even rural programs such as agricultural credit, will readily win over persons whose friends or relatives have been killed or injured by aerial attacks. These people are more likely to volunteer for the VC.


Interdiction strikes are most effective where enemy forces, supply lines, and logistics are highly organized, well defined, and hence vulnerable to air attack. This is not the case in Viet-Nam. Air interdiction is basically a conventional war concept, and to be valid, interdiction strikes require clearly defined enemy territory. We are not prepared to admit that parts of Viet-Nam are enemy territory.

The French experience suggests, in fact, that air interdiction is not a useful concept in this kind of warfare. There is no question that air power is useful against the VC and that they are afraid of it. But the best use of air power may be strictly limited to relief of units, posts, and hamlets under attack, the great mobility which air power provides, and carefully controlled close air support of government operations.


While targeting has certainly been improved, it is probably not susceptible to adequate refinement. This is because many Vietnamese officials frankly do not recognize the basically political nature of this war. The province and district chiefs, who are the primary sources for much of the intelligence on which interdiction strikes are based, are inadequately trained and often do regard certain areas as enemy territory simply because they are known to harbor VC.

In this connection, we note (Embtel 1553, June 4, 1962)2 that in June of last year we undertook a very large attack involving B-26s, AD-6s and T-28s against “confirmed command post installations, facilities and activities” in I Corps. The coordinates reported for the strike zone covered an area of about 230 square miles.

The prestige of the U.S. in Asia can be seriously damaged if it becomes widely known that American aviators are killing Vietnamese peasants. The Communist nations have already started to make this a serious part of their propaganda campaign. We may be able to explain that defoliants are weed killers, but we cannot expect to explain why American pilots are using bombs, napalm, and machine guns against Vietnamese peasants in a war where our role has been publicly defined as limited to training, equipping, and supplying the Vietnamese in the prosecution of their own defensive war. For ourselves and for the Vietnamese the most important rule governing our actions is to avoid steps which will create the general belief that this is our war. We are already getting too close to such a position.
Our actions in undertaking a direct combat role in Viet-Nam are in violation of the Geneva Accords.
It appears that the U.S. role in interdiction-strikes badly stretches, if it does not actually break, the mandate under which American air power was first engaged in the Viet-Nam conflict.

NSAM 111 of November 22, 1961,3 authorized U.S. uniformed personnel “for air reconnaissance, photography, instruction in and execution of air-ground support techniques, and for special intelligence.” Present interdiction missions appear to go beyond “air-ground support techniques”.

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The arguments set forth above indicate there is not a demonstrably clear case either for or against interdiction missions, and this in itself is a convincing argument for undertaking a review. While some of the issues involved transcend the situation in Viet-Nam itself, such a review requires an on-the-ground evaluation of the validity of arguments advanced above, pro and con, and some indication of the respective weights to be assigned them. In such an evaluation, we think the intimate interaction of political and military factors must be taken into account. A measure, for instance, which gave short-run military advantages might in the long run be militarily disadvantageous if it affected popular attitudes in such a way as to increase Viet Cong ability to build larger forces and the organization required for their effective support. What we would hope to determine is the net worth, positive or negative, of (a) U.S.-piloted interdiction and (b) interdiction missions piloted only by Vietnamese.

On receipt of your comments and information, we intend to review the problem thoroughly and come to a decision.4

  1. Source: Department of State, Central Files, POL 26-1 S VIET Top Secret; Priority. Drafted by Heavner and Wood, cleared by Harriman and Hilsman. Repeated to CINCPAC for POLAD. JCS and DOD/ISA were informed of the contents of the message.
  2. Telegram 1553 from Saigon conveyed a summary of an intelligence briefing conducted in Saigon on June 1. (Ibid., 751K.00/6-462)
  3. For text, see Foreign Relations, 1961–1963, vol. I, Document 272.
  4. In telegram 917 from Saigon, April 16, Nolting responded that the Embassy was “coordinating with MACV an extensive review all aspects air interdiction. Because of vital importance this subject to effort here in Vietnam, believe thoroughness preferable to speed. I hope be able respond definitively within very near future.” (Department of State, Central Files, POL 26-1 S VIET)