100. Airgram From the Embassy in Vietnam to the Department of State1



  • Interdiction


  • CA-103622

For Harriman and Hilsman from Nolting. In response to the reference instruction, my staff and I, with the close cooperation of MACV and 2nd Air Division, have conducted a thorough review and evaluation of the subject of interdiction air strikes. The results of this study are presented below.

General Description of the Problem.

During the past six months about 7,000 combat support sorties, or a little more than 1,000 per month, have been flown in SVN. About 2,500 of these, or 35%, have been flown by Farmgate (combined US/VNAF crews). Of these 7,000 combat support sorties, VNAF has flown about 1,900 interdiction missions, while Farmgate aircraft have flown about 600 such missions. Thus, Farmgate has flown about 415 combat support sorties per month over the past six months, of which about 100 per month have been interdiction missions. Accordingly, Farmgate combat support sorties have amounted to about 35% of the total such sorties flown in SVN over the past six months, while Farmgate interdiction sorties have counted for less than 10% of that total.

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There are three general types of interdiction targets involved in the war against the VC:

Structures abandoned by people relocated into strategic hamlets. The purpose of pre-planned interdiction missions against such structures is to deny the VC their use as dwellings, food storage, training centers, arms factories, ordnance storage, etc.
Structures abandoned by the VC during ARVN operations against them. Immediately following the operation, and after GVN forces have withdrawn from the area, ARVN often requests an air strike to destroy the remaining structures.
Targets of known VC concentrations, headquarters, storage areas, communications and control centers, arms manufacturing facilities, etc. These targets are normally located in remote areas where the air interdiction mission is the only feasible method of destroying them.

Of these three types of targets, only the third kind is likely to be inhabited at the time of an interdiction mission against it. Because of the remote areas in which targets are normally located, however, interdiction strikes against them are unlikely to affect many people who might be classed as “innocent bystanders.” To be sure, these target areas could harbor some people who were not wholehearted V(: supporters or who might even be basically anti-VC. It is highly doubtful, though, that the numbers of such persons are great enough in proportion to the total numbers of people in SVN affected by all GVN and VC military operations to have any important effect on the GVN’s efforts to gain control over and support of the mass of the population.

The basic source of intelligence for interdiction target selection is GVN knowledge of those areas under VC control or in which VC influence is predominant. This knowledge is gained from secret agents in GVN employ at different levels; interrogation of VC prisoners and defectors; captured VC documents; patrolling and scouting by ARVN, Rangers, Special Forces and paramilitary units; after-action surveillance of withdrawing VC to obtain information on escape and dispersal routes; VC ground fire; and photo reconnaissance. Sometimes, intelligence gathered from one or more of these sources has such a high reliability that a valid target can be established immediately. When, however, intelligence is fragmentary or has a lower evaluation rating, additional confirmatory evidence is sought by employing one or more of the sources mentioned above, as well as by photo reconnaissance flown specifically for target location and evaluation. Any time lag ensuing from this process requires revalidation of the target.

In many cases, the information provided by local civil GVN authorities establishes the basic requirements for an interdiction mission. This information is passed by civilians through the village and district chiefs to the Province Chief, who passes it to the GVN military authorities. Interdiction target requests originating with the local civilian authorities must be passed at least to Corps level for approval; target [Page 249] requests originating at the Corps level or higher must be passed to the local authorities to confirm the validity of the target. While the mechanism for approving interdiction targets varies slightly from Corps Hqs. to Corps Hqs., all such targets must be approved at the Corps level.

Additional requirements for target identification and attack are effective target marking, two-way radio communications, and trained Vietnamese forward air controllers, all of which must without exception be employed before Farmgate aircraft are authorized to attack an interdiction target. Final discretion for carrying out interdiction missions rests with the pilot. There are many cases on record of both Farmgate and VNAF pilots refraining from attacking targets because of inadequate target visibility, communications failure, inadequate target markings, and apparent discrepancies between the target as seen by the pilot and as described in the target folder. Pilots returning to base having refrained from delivering ordnance for these reasons are not charged with failure to carry out their missions. They are debriefed and the results of their observations are fed back into intelligence channels for verification and necessary correction of targets.

No one would claim that the sources of intelligence on which target selection is based are faultless. Nevertheless, as described above, raw intelligence is subjected to such painstaking scrutiny and confirmation at all levels before a target is approved and actually attacked that the risks arising from Vietnamese carelessness or insensitivity are considered to be minimal. Parenthetically, the stringent requirements and controls imposed on Farmgate interdiction missions have been adopted by the GVN and greatly improved VNAF operations and procedures.

It is admittedly difficult to obtain accurate and complete information on the casualties caused by interdiction strikes. Nevertheless, positive official evidence is available in only one case to confirm that innocent people have been killed or injured in interdiction strikes. It should be noted that this case was attributable to serious pilot error rather than to faulty intelligence or improper target selection. Reports of other such incidents are occasionally received; they are investigated but have not been confirmed. There is certainly no evidence to suggest that the relatively small number of Vietnamese affected by interdiction missions react more adversely to the GVN than do the many more affected by all types of GVN and VC military operations. It also seems highly questionable to conclude that individuals affected by Farmgate or VNAF interdiction strikes, even if these individuals are basically anti-VC or at least less than wholehearted VC supporters, are going to become sympathetic to the VC. Just as good an argument to the contrary might be made: individuals who are half-hearted supporters of the VC or who are forced by circumstances to work for the VC could regret the circumstances which exposed them to the strikes, and blame [Page 250] the VC for these circumstances; they could fear those strikes more than they resent the perpetrators of the strikes. Indeed, there is more evidence to support this argument than the contrary one. One of the generally accepted major reasons for the large-scale Montagnard flight into GVN-controlled areas over the past year has been their fear of being caught between VC and GVN military operations, including air strikes. Their reaction generally was not to go deeper into VC territory but to flee VC-controlled areas in search of GVN protection. Similarly, in a more recent case, it appears that the 1,300 or more refugees of Khmer-origin who recently fled an area long controlled by the VC in the Tri Ton District of An Giang Province to receive GVN protection did so because the area near where they had been living had just prior to their flight been subjected to heavy and sustained air strikes against the VC. These people who have sought GVN protection have undoubtedly made no conscious political choice between the VC and the GVN; rather they have sought safety and decided that safety lay with the GVN rather than with the VC.

As indicated above, less than 10% of the combat support sorties flown in SVN in the past six months have been interdiction missions flown by Farmgate aircraft. These aircraft, of course, have VNAF markings. As was originally stipulated in the rules of employment of Farmgate aircraft, they are employed in combat support missions only when the VNAF capability is exceeded. Despite frequent press reports on the role of USAF personnel in combat support missions, there is no more emphasis on that role than on the role of the US Army advisers attached to ARVN combat units. There is thus no foundation for believing that US participation in interdiction missions could intensify the Communist charges of US control over the war in SVN or of the GVN’s “neo-colonial” subservience to the US.

Pros and Cons

The analysis above is intended to place the subject of interdiction air strikes in proportion within the overall context of the GVN’s war against the VC and of the GVN’s efforts to win the support of the population. It obviously attaches more weight generally to the pro arguments in the reference instruction than to the con arguments, largely because the latter are reduced in importance when applied to the subject of interdiction in its proper context as we see it. Nevertheless, it is believed useful to make some specific comments on the Department’s pro and con arguments.

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Regarding the first pro argument, intelligence reports confirm that the interdiction effort restricts VC movements, the consolidation and storage of VC arms, equipment, food and other supplies. Interdiction; strikes also restrict the manufacture of VC war goods, keep the VC forces off balance, disrupt training centers, render medical attention more difficult and lower morale. In short, the destruction of interdiction targets restricts the flow of war materiel to VC forces, which in turn reduces their capability to fight.

A key pro argument has been omitted from the reference instruction. Farmgate interdiction missions constitute about one-fourth of the interdiction missions in SVN. To reduce Farmgate participation in such missions before VNAF has the capability to fulfill the requirements and at a time when operations against the VC are being intensified in accordance with the National Campaign would deprive the GVN of an important military advantage. Undoubtedly, the plan of ground operations under the National Campaign would have to be restudied and reduced in scope, resulting in a prolongation of the war. Similarly, the political impact of a Farmgate curtailment at this time on US-GVN relations is likely to be considerable.



As the above statement of the problem would suggest, con arguments 1, 2, 5 and 6 are so general that they might be applied across the board to all types of GVN military operations. To use them against a specific aspect such as interdiction gives those arguments much more importance than they should have in relation to the pro arguments. One might ask, for example, that if Farmgate interdiction missions were ruled out, would the GVN be better able to win the support of the population? Would the VC be able to recruit with much less ease? In our judgment, the answer to both of these questions is no.

In this connection, it may be a dangerous oversimplification, as con argument 1 asserts, to regard any SVN territory as enemy or any village as VC. However, it is an equally dangerous oversimplification to consider that there are no hard and fast VC targets, base areas, training and supply centers, etc., which can be destroyed by air interdiction without endangering the lives of innocent people. Such areas are frequently revealed by GVN military sweeps and patrols, and increasingly, through intelligence provided by defectors and POW’s. Post-strike inspections on the ground have frequently verified the accuracy of the intelligence and the effectiveness of the strikes.

It is the considered military judgment here that con argument 3 is not valid, since the extent or magnitude of the target, or its relationship to a battle line, does not matter. In the judgment of MACV, with [Page 252] which I agree, once a target is verified, it is just as legitimate in counterinsurgency warfare as in a limited or general conventional war. We are therefore unaware of any reason why interdiction missions are more applicable to conventional warfare then to counterinsurgency warfare, although we are fully conscious of the greater difficulty of fixing targets in this type of situation.

Regarding con argument 4, it is granted that targeting techniques cannot be refined to as great a degree as would be ideal. It may also be admitted that certain Vietnamese officials are not as sensitive to the basically political nature of the war, and therefore are not wholly trustworthy as sources of information for interdiction target selection (province officials and ARVN military officers vary widely in this regard). However, in absolute terms, target selection techniques currently employed in SVN are applied with great care and with many safety devices. Moreover, it must be recognized that, largely because of the USAF advisory effort and Farmgate operation, VNAF techniques of target selection, marking and operational control have been tightened up and improved considerably.

In this connection, there appears to be a misconception as to what an interdiction target is. It is not an area, but a pinpointed facility or troop concentration. Thus, even if a province or district chief considers an area as enemy territory simply because it harbors VC, the interdiction strike is conducted, not against an area but against a specific verified target—a target which is usually in a remote area. The 230mile area referred to in the reference instruction was not the target but the target area. In that area there were 19 pinpoint targets of which 12 were hit and 7 were not hit because of weather. The incident referred to was caused by pilot error.

Regarding con argument 7, Farmgate aircraft are today operating under the same ground rules that were established when they arrived in Viet-Nam. There has been no change in those rules. Two changes have occurred, however, since Farmgate first arrived in SVN: 1) the number of Farmgate aircraft has increased to meet increased requirements and the tempo of air activity has increased; and 2) the press has gradually devoted more attention to the role of air power in Viet-Nam’s war.


US-piloted interdiction missions, at the present stage of the war in SVN, are a necessary supplement to VNAF’s interdiction capability, which is growing but is still insufficient to fulfill the intensified requirements of the National Campaign. Total Farmgate and VNAF capabilities are still at times exceeded by these requirements. Intelligence [Page 253] reports confirm that the present combined interdiction effort of Farmgate and VNAF is restricting VC capabilities through the destruction of VC troops, arms, equipment and supplies.

The continued refinement of target selection, marking and operational control techniques has reduced insofar as possible the likelihood that interdiction missions will cause casualties among innocent civilians or among people who are not wholehearted VC supporters, although there is no way to ensure that interdiction missions will avoid such casualties altogether. There is, on the other hand, considerable evidence that those threatened by air strikes and other combat operations have found that the way to escape danger is to seek GVN protection. The GVN has not thereby won their loyalty, but it has won control over them and the opportunity to win their loyalty, and it has denied them, their resources and their energies to the VC. Against this, there is very little concrete evidence available to give weight to the argument that interdiction missions, more than other kinds of combat operation, will render more difficult if not impossible the GVN’s task of winning the loyalty of the people. To curtail or withdraw Farmgate interdiction operations on the basis of very little negative evidence when the positive evidence of their effectiveness is much greater would, in my judgment, be a mistake. It would render more difficult and lengthy the task of restoring internal security to SVN, give the VC an advantage it does not now have, and raise questions in the GVN as to US support.

The fundamental questions raised in the reference instruction have been on our minds here for a long time. It is certainly useful to have made another mission-wide assessment of this particular problem. I have myself been on the look-out for many months, and have had many discussions to try to evaluate the net effects of many types of military operations, not alone air operations. The yardstick used is winning the people. The best evidence, I think, is found in captured VC documents and in POW and defector testimony. Among these, I have seen nothing to indicate or suggest that the VC think that air strikes are helping to win the struggle for them. On the contrary, all the evidence from VC sources is in the opposite sense.

F.E. Nolting, Jr.
  1. Source: Department of State, Central Files, POL 26-1 S VIET Top Secret. Drafted by R. H. Miller and cleared by Manfull and General Harkins. Repeated to CINCPAC for POLAD.
  2. Document 66.