Saigon, August 23, 1968, 1304Z.
MAC 11409. The questions you have posed come at a very important time.2These questions were transmitted in CAP 82092 from Rostow, August 23. (Ibid.) In an August 19 memorandum to Clifford, Rostow argued that Hanoi would increase significantly its southward infiltration if the United States halted the bombing. (Johnson Library, Alain Enthoven Papers, Bombing of North Vietnam) In critiquing Rostow's assertion in a memorandum to Nitze, August 22, Enthoven, noting that the bombing did not impair the NVA/VC in the South from receiving adequate supplies and reinforcements, instead argued that North Vietnam would reduce its infiltration in accordance with a reduction in its attritional losses after an end to the bombing campaign. (Ibid.) We are convinced that the enemy has determined to make, over the next days and weeks, the maximum military effort of which he is capable at this time. Because the bombing over the North Vietnamese Panhandle is so linked to the military effort he can make in South Vietnam, I am happy that you have posed the questions and that I can address them now.
Question 1: What is the effect of our current bombing operations in North Vietnam?
Several effects are of importance. One is the destruction of materiel itself. We believe we are now destroying or damaging approximately 15 per cent of the trucks believed to be moving into South Vietnam. This amounts to an average of 90 trucks per week. Second, and of greater importance, is the reduction we have caused in the number of trucks moving. While other factors may also be at work, it is our conviction that the air interdiction program in the North Vietnam Panhandle has been the primary agent which has reduced trucks detected from a level of 1000 a day in mid-July to between 150 and 200 a day at the present time. A third effect is to prevent the enemy from massing artillery and air defense means in the area to the north of the DMZ form which they can attack our forces. Further, we interfere with his ability to concentrate forces and supplies for sudden attacks through the DMZ against our units. There are, of course, other effects such as pinning down many thousands of essential air defense and LOC support forces.
Question 2: What would be the military effect of a cessation of the bombing?
Again, there are several important effects. First, military materiel (much of it POL and ammunition, as fires and secondary explosions testify) would be able to reach the DMZ or the borders of Laos unimpeded. We believe the current attrition from truck destruction alone, not to mention truck park storage areas, is running several hundred tons per week on the average in the NVN Panhandle. Second, the truck flow could be expected to return to a level of 1,000 a day or even higher within as little as a week. If we take average truck loading at 3–1/2 tons, we are talking about an increase, repeat increase, in southward movement which could amount to 1,500 tons per day or more. Next, the enemy would be able to mass artillery, air defense means, and ground units freely north of the DMZ for use against our forces. He could deploy his air force into areas north of 17 degrees from which to threaten or attack our forces and installations throughout much of South Vietnam. He would be able to reopen his railroad as far south as Vinh and subsequently to Dong Hoi. He would thereby free additional numbers of trucks to support his forces in the south. Finally, freed from interdiction north of 17 degrees, the enemy could move reinforcements to the DMZ by truck or rail thus drastically shortening transit time.
Question 3: Since March 31 what is the average number of trucks destroyed and trucks damaged per week? What is the average number of trucks sighted in the Panhandle per week? We are aware of the difficulties, but what is your best estimate of the total number of trucks (sighted and unsighted) that flow through the Panhandle each week and the proportion of this total that we are now getting?
As indicated above, we are currently averaging about 90 trucks destroyed and damaged per week since 31 March. The average number of trucks detected in the Panhandle per week has been 1300. Our best estimate of total number flowing into the Panhandle each week during that period is 620. We estimate that we are destroying or damaging 15 per cent of these. I would like to emphasize however that, as indicated above, we believe the major impact of our bombing effort is found in the reduction of truck flow, rather than in the numbers actually destroyed.
Question 4: What is the estimate of military casualties we inflict on the enemy each week in the bombing of North Vietnam?
The military casualties resulting from our bombing efforts are obviously extremely difficult to estimate with any confidence. Destroyed and damaged trucks probably account for some 200 casualties (KIA and WIA) weekly. Also, nearly one-half of the 235 weekly road interdictions we are averaging occur at night when road crews are present. There are undoubtedly substantial casualties among road repair/maintenance crews and also among air defense crews, but any estimate would be extremely speculative. A figure of 5 to 10 thousand per month does not seem unreasonable. However, military casualties in North Vietnam are not, in my judgment, the most significant measure of the effectiveness of our bombing. As indicated above, its major effects lie in reducing the weight of effort that can be directed against our forces.
Question 5: Is there any possibility of your providing for the President even an approximate estimate of the additional casualties we would take if we stopped the bombing of North Vietnam?
During the period May through July this year we have been sustaining in the fighting in I Corps losses amounting to an average of 240 killed in action each week. Approximately 70 percent of these have been U.S. The intensity of enemy action, i.e. the scale and duration of combat in which his units are involved, is a direct determinant of the magnitude of our losses. Assuming that the cessation of bombing would be reflected in a several-fold increase in his logistic capability to support combat, and in the intensity of combat, we would have to expect a several-fold increase in U.S. and allied casualties in I Corps. With the bombing authority now in effect, I am able with forces available to limit the enemy's capability in South Vietnam by interdicting his roads and destroying substantial amounts of his munitions and supplies before they reach South Vietnam. In addition, I am able to suppress his artillery and air defense north of the Ben Hai so that our positions just south of the DMZ are secure. If the bombing in North Vietnam now authorized were to be suspended, the enemy, in 10 days to two weeks, could develop a capability in the DMZ area in terms of scale, intensity and duration of combat on the order of five times what he now has. If he should develop this, it would, in my judgment, make our positions in northern Quang Tri to include Dong Ha and the Cua Viet untenable. I cannot agree to place our forces at the risk which the enemy's capability would then pose.3In an August 23 memorandum to Rusk, Bundy criticized the facts and conclusions that Abrams reached in his telegram. First, the reduction in numbers of trucks moving southward was likely related to heavy flooding. Second, in the event of a bombing halt, it was not likely that the DRV could increase the flow of tonnage by an additional 1,500 tons per day. Third, casualty rates far exceeded any past predictions by the CIA. Fourth, Bundy doubted that the enemy could multiply his logistical capabilities by a factor of five and would hesitate to increase his capability since bombing would resume if such an increase was detected. “I find these responses a highly exaggerated and tendentious presentation,” Bundy concluded. (National Archives and Records Administration, RG 59, S/S Files: Lot 72 D 192, Dean Rusk White House Correspondence, PR-Hold-Vietnam-FE) Similar criticisms of the supposed factual errors and logical fallacies in Abrams' response are in memoranda from Warnke to Clifford, all dated August 29. (Washington National Records Center, Department of Defense, OSD Files: FRC 330 73 A 1304, 1968 Secretary of Defense Files, VIET 092.2) In an undated memorandum to Wheeler, Clifford also was critical of Abrams' telegram. (Johnson Library, Alain Enthoven Papers, Bombing in North Vietnam) Warnke's analysis of both Rostow's memorandum and Abrams' telegram are in an August 30 memorandum to Clifford. (Ibid.)