Foreign Relations of the United States, 1964–1968, Volume IV, Vietnam, 1966

36. Memorandum From Secretary of Defense McNamara to President Johnson ¹

Washington, January 24, 1966.

SUBJECT

• The Military Outlook in South Vietnam

You have asked for my comments on the outlook for military operations in South Vietnam. This memorandum addresses that question.

1. Expansion of Forces and Levels of Operation. The following statistics summarize our best estimates of force levels and operational rates for the next twelve months:

		June ʼ65	Dec ʼ65a	June ʼ66	Dec ʼ66
Strength
VC & PAVN:	Men	187,000	236,900	?	?
	Batns	63	107	150	155
RVN (excl police):	Men	522,400	573,000	631,457	661,000
	Batns	128	133	168	173
US:	Men	59,900	178,800	b277,800	b c378,800
	Batns	9	34	46	75
3d Country:	Men	3,300	22,400	38,000	44,600
	Batns	1	10	19	23
Aircraft
US Fixed wing (in SEA)		886	1,487	1,684	1,879
Helicopter		508	1,483	1,853	2,391
Attack Sorties per Month
NVN:	Sorties	2,401	2,198	4,000	4,000
	Losses	9	12	18	18
SVN	Sorties	7,234	13,114	12,000	15,000
	Losses	6	9	8	12
Laos	Sorties	511	3,047	4,500	4,500
	Losses	2	3	4	4
Total		10,146	18,359
Tons Dropped		30,510	31,341	51,500	68,800

a December activity figures are reduced by Christmas Cease-fire and Pause.

b The JCS believe that it would be necessary to have a selective call-up of reserves and a selective extension of terms of service to achieve the personnel strengths shown at the times indicated.

c Would rise substantially above this if estimates of CINCPAC are accepted.

2. The Enemy Force Build-up. The Communists appear to have decided to increase their forces in South Vietnam both by heavy recruitment in the South (especially in the Delta) and by infiltration of regular North Vietnamese forces from the North. The infiltration from the North is mainly by truck. It is on greatly improved routes—routes, some of which are new and some of which have been widened, or upgraded for truck use, or all-weathered, or built to by-pass points vulnerable to choke-point bombing, or constructed under jungle canopy and bamboo-trellised camouflage to prevent aerial observation.

General Westmoreland estimates that, through 1966, North Vietnam will have the capability to generate and infiltrate 3 regiments (9 battalion-equivalents, or 4500 men) a month, and that the VC in South Vietnam (now with 85 battalion-equivalents) can recruit and train 7 new battalion-equivalents a month—together adding 16 battalion-equivalents a month to the enemy forces. Despite serious attrition—desertions and increasing combat casualties—the enemy can be expected to enlarge his present strength of 107 battalion-equivalents to more than 150 battalion-equivalents by the end of calendar 1966, when—by our deployments and aggressive strategy—hopefully his losses can be made to equal his input.

3. The Enemyʼs Supply Requirement. The 107 battalions of PAVN and VC forces in South Vietnam need only 20 or so tons a day of supplies from North Vietnam to sustain “1964” levels of activity and only approximately 80 tonsʼ a day to sustain “light combat” (1/5th of the force in contact once every 7 days using 1/3d of their basic load). The requirements from the North after the expansion of enemy forces to 150+ battalions at end of 1966—assuming that the enemy refuses, as it can, to permit the level of combat to exceed “light”—should approximate 140 tons a day.

4. The Enemyʼs Supply Capability. As for the Communistsʼ capability to supply their forces in the South, it is clear that our program of bombing North Vietnam has caused them difficulties. It has destroyed many of their infiltration-oriented facilities (e.g., bridges, roads, railroads, trucks, rolling stock, barracks, storage centers, etc.), increasing the cost and difficulty of infiltration of both men and materiel. There is evidence that the volume of infiltration that the system could otherwise handle has been halved; that approximately 50–100,000 men have been diverted from normal activities to defense and repair work; that government activities are being decentralized, causing inefficiencies and political risks in a totalitarian state; that mobility within North Vietnam has been reduced; and that the reduction in enemy initiatives in Laos may be attributable to their need to husband their resources for their South Vietnam effort.

Nevertheless, despite our anti-infiltration efforts at pre-Pause levels, it is estimated that the enemy is capable of generating in the North and infiltrating to the South not only the 4500 men a month mentioned above, but an average of 200 tons of supplies a day depending on the season—considerably more than the perhaps 40–140 tons a day required to maintain activities at “1964” to “light-combat” levels.

5. The US Interdiction Capability. It is not clear that the US 1966 bombing program will cut the flow of men and materiel from the North to the South to a point below the VC/PAVN minimum needs. It is clear that the success of the interdiction program is contingent upon a cumulative and sustained effort. The interdiction can be while the supplies are en route into North Vietnam from the outside world, inside North Vietnam, en route from the North by sea or through Laos or Cambodia to South Vietnam, or inside South Vietnam; it can be by destruction or slow-down; the effectiveness can be prolonged by exhausting the Northʼs repair capability, and can be enhanced by complicating their communications and control machinery. At a minimum the bombing program against North Vietnam should include 4000 attack sorties a month as compared with 3125 in the month of November 1965 before the Pause, intensive day-and-night armed reconnaissance of road and rail lines of communication throughout North Vietnam (except for the cities and the strip alongside China), and destruction of POL storage targets. (The efforts in North Vietnam are to be added to intensified bombing of the lines of communication in Laos, tight surveillance of the sea, increased efforts on the Mekong and Bassac Rivers from Cambodia, harassment of the lines of communication in South Vietnam, and destruction of base areas in South Vietnam.)

Recognizing that the estimates as to enemy needs and capabilities and as to our interdiction results may be wrong by two either way, all that can be said now—before some studies are completed—is that the increased program probably will not put a tight ceiling on the enemyʼs activities in South Vietnam, but probably will reduce the flow of supplies to the point where the enemy receives too little for full flexibility and for frequent offensive actions, too little to defend themselves as often against aggressive US/GVN forces, and too little to permit Hanoi to continue to deploy forces with complete confidence that they can be supplied.

Furthermore, as very important by-products, the program will keep the pressure on North Vietnam—to condition them toward negotiations and an acceptable end to the war—and will maintain the morale of our South Vietnamese allies.

6. The US Force Build-up. The US force build-up plan is to deploy additional US and third-country forces, raising the battalion strength from 44 in December ʼ65 to 98 in December ʼ66. This should do several things. According to General Westmorelandʼs estimates, the deployments of the additional forces will:

a. Result in destruction of one-third of the enemyʼs base areas, i.e., in-country resources.

b. Permit friendly control of just under one-half, as compared with the present one-third, of the critical roads and railroads.

c. Attrite VC/PAVN forces at an increasing rate, leading to the leveling off of enemy forces at the 150+ battalion level mentioned above (provided the Chinese do not supply “volunteers”).

d. Ensure that friendly bases and government centers are defended under any foreseeable circumstances (though some district towns may be overrun and have to be retaken).

e. Lead to government control of an estimated 50 per cent of the population.

(In this last connection, Prime Minister Ky has stated that the Government now controls 25 per cent of the population and that it will take two years to raise the control to 50 per cent. The Mission and the Government have just initiated a 4-area priority pacification effort—emphasizing the Danang (389,000), Qui Nhon (650,000), Hoa Hao (800,000), and Saigon (3,500,000) areas. They believe that, taking account of the concentration of effort and resources required to make progress in pacification, these quite limited areas are all we can hope to handle during the next year.)

7. Evaluation. The situation at yearʼs end could be either better or worse than implied by the above information. The reported drop in enemy morale and in quality of his recruits together with interdiction successes and continuity of the Ky government could lead to the start of snow-balling in our favor before December. On the other hand, if the enemy force build-up is as predicted and if attrition of that force and of its supplies fall short, we could find ourselves “behind the power curve” going into 1967; we could be faced with the requirement to deploy at least an additional 3-division corps (27 battalions) in 1967.

Our intelligence estimate is that the present Communist policy is to continue to prosecute the war vigorously in the South. They continue to believe that the war will be a long one, that time is their ally, and that their own staying power is superior to ours. They recognize that the US reinforcements of 1965 signify a determination to avoid defeat, and that more US troops can be expected. Even though the Communists will continue to suffer heavily from our ground and air action, we expect them, upon learning of any US intentions to augment its forces, to boost their own commitment and to test US capabilities and will to persevere at a higher level of conflict and casualties (US killed in-action with the recommended deployments can be expected to reach 1000 a month.)

If the US were willing to commit enough forces—perhaps 600,000 men or more—we could probably ultimately prevent the DRV/VC from sustaining the conflict at a significant level. When this point was reached, however, the question of Chinese intervention would become critical. (We are generally agreed that the Chinese Communists will intervene with combat forces to prevent destruction of the Communist regime in North Vietnam; it is less clear whether they would intervene to prevent a DRV/VC defeat in the South.) The intelligence estimate is that the chances are a little better than even that, at this stage, Hanoi and Peiping would choose to reduce the effort in the South and try to salvage their resources for another day.

It follows, therefore, that the odds are about even that, even with the recommended deployments, we will be faced in early 1967 with a military stand-off at a much higher level, with pacification hardly underway and with the requirement for the deployment of still more US forces.²

RMN ³

1. Source: Johnson Library, Warnke Papers, McNaughton Files, McNTN VII, Late Vietnam. Top Secret. Neither the original nor a copy of the memorandum has been located in the White House files at the Johnson Library.

2. The Joint Chiefs of Staff believe “that the evaluation set forth in paragraph 7 is on the pessimistic side in view of the constant and heavy military pressure which our forces in Southeast Asia will be capable of applying. While admittedly the following factors are to a degree imponderables, they believe that greater weight should be given to the following:

   • “a. The cumulative effect of our air campaign against the DRV on morale and DRV capabilities to provide and move men and material from the DRV to South Vietnam.
   • “b. The effects of constant attack and harassment on the ground and from the air upon the growth of Viet Cong forces and on the morale and combat effectiveness of Viet Cong/PAVN forces.
   • “c. The effect of destruction of Viet Cong base areas on the capabilities of VC/PAVN forces to sustain combat operations over an extended period of time.
   • “d. The constancy of will of the Hanoi leaders to continue a struggle which they realize they cannot win in the face of progressively greater destruction of their country.” [Footnote in the source text.]

3. The source text bears these handwritten initials indicating McNamara signed the original.