Foreign Relations of the United States, 1969–1976, Volume VII, Vietnam, July 1970–January 1972

159. Memorandum From the President’s Assistant for National Security Affairs (Kissinger) to President Nixon¹

Washington, March 20, 1971.

SUBJECT

• Lam Son

You will be asked for your assessment of the Lam Son operation.² Thus far the effects of Lam Son have been viewed in the overly simplistic terms of whether trucks are moving on the Ho Chi Minh Trail. We know trucks are moving, though at a substantially reduced rate south of operational areas. Lam Son was never intended to stop the movement of trucks.

What is fundamental to an assessment of Lam Son, however, is what the ultimate effectiveness of the movement of these trucks is in terms of the enemy’s ability to continue or escalate the war in South Vietnam and Cambodia. If the trucks are supplying troops in South Laos, then they cannot be moving supplies to troops in South Vietnam or Cambodia.

On these grounds, there are some rather striking conclusions to be drawn about the effects of Lam Son.

We assume that at the beginning of this year enemy supplies were low and that his supply effort last year roughly approximates the logistics flow that will be required to support a protracted war in 1971.

But we know that in 1971 the enemy must meet a long list of new demands on his logistics system in addition to the output he achieved last year. These new demands must be met merely to sustain a protracted war in 1971.

The new demands are the supply increases necessary to compensate for:

—(1) the loss of Sihanoukville,

—(2) new logistics demands for non-combat consumption to support the greatly enlarged force structure stationed in South Laos in fear of the kind of operation Lam Son has proved to be,

—(3) new demands for combat consumption by enemy troops defending the trail against Lam Son,

—(4) the tonnages of supplies in caches destroyed by Lam Son,

—(5) increased tonnage destroyed by bombing in the 1970–71 dry season versus the 1969–70 dry season.

The loss of Sihanoukville alone placed an enormous additional logistics burden on the Ho Chi Minh Trail. At least one-third and possibly one-half of the enemy’s supply requirement for South Vietnam was met by shipments through Sihanoukville and purchases on the Cambodian economy.³

If the tonnages formerly shipped through Sihanoukville go down the Trail they must be multiplied by a factor of four to five to arrive at the total tonnage necessary to feed the additional logistics and combat troops in South Laos, to supply the POL for trucks, etc.

When all of these new requirements are added together—to offset Sihanoukville, direct consumption and destruction caused by Lam Son, etc.—they indicate that the enemy must increase his trail input effort by at least 50% this year merely to come out where he did last year. His trail output must be about one-third more than last year’s.

Yet, to date we are reasonably confident that output from the trail into South Vietnam and Cambodia is only one-third last year’s output.

It is too early to say what the final results will be, but we do know that:

• —Even a record enemy logistics effort through the rest of the dry season, starting today, is likely to leave the enemy significantly short of the supplies he needs in 1971 to conduct a protracted war effort. This means major offensives of country-wide impact are unlikely. It means the Vietnamese government will have the opportunity in 1971 to continue to achieve pacification gains against a low level of enemy activity.⁴
• —Supplies will arrive too late for offensive activity in the 1971 dry season, the usual time of enemy highpoint activity. Thus far in 1971 enemy activity in Cambodia and South Vietnam has fallen below that of similar periods in past years.
• —The enemy will have fewer options in 1972. Because it takes several months of the dry season to attain a logistics outflow rate to Cambodia and South Vietnam, the failure of the enemy to build up large stockpiles in 1971 will mean that it will be late in the dry season (the dry season ends about May 15) or into the wet season in 1972 before his logistics capabilities would permit him to launch a major offensive. This, of course, assumes the enemy can successfully solve the logistics problems in 1972 he was unable to solve in 1971.
• —Local supply shortages minimize possibility of major offensives this year in MR 2 and MR 1 except across the DMZ where the enemy is not logistically constrained. Lam Son would appear to have preempted an MR 1 or MR 2 offensive this dry season by preventing the enemy from establishing forward-based stocks in northern South Vietnam and the adjoining Laos border areas.

While the logistics benefits to Lam Son are very important, another key result of the operation was that it made credible the threat Hanoi has maintained up to 30,000 combat forces in South Laos in 1970 to meet. Hanoi must maintain large forces in South Laos to protect its logistics corridor as long as friendly forces pose a credible threat to the Trail.

Thus, a key long range benefit to Lam Son is that the enemy will feel some compulsion to continue to maintain large combat forces in South Laos.⁵ Therefore, these forces (a portion of which were formerly in South Vietnam) cannot be used to threaten Vietnamization in South Vietnam.

A near term benefit to Lam Son is that enemy units destined to conduct offensive activity in Cambodia and the highlands of South Vietnam have been held up to cope with ARVN. A possible four enemy regiments have been put out of combat commission by Lam Son. These results complement the logistics benefits to Lam Son in making it unlikely that the enemy will mount major offensive activities in MRs 1 or 2 of South Vietnam and in Cambodia, despite evidence that the enemy planned to mount such offensives.

The assumptions and calculations underlying the estimates in this memorandum are at Tab A.⁶

1. Source: National Archives, Nixon Presidential Materials, NSC Files, Box 82, Vietnam Subject Files, Vietnam Operations in Laos and Cambodia, Vol. V. Top Secret. Sent for information. A stamped notation reads, “President has seen.” According to a March 27 memorandum from Kennedy to Kissinger, the President requested that a summary of this memorandum be sent to Congressmen Boggs, Albert, and Ford. (Ibid., Box 314, Subject Files, Congressional Jan–Jul 1971, Vol. II [2 of 2]) Haig also sent a modified version to Klein under an April 15 covering memorandum authorizing him to share the information with columnist Jack Anderson. (Ibid., Box 154, Vietnam Country Files, Viet 9 Apr 71–30 Apr 71)
2. Presumably at the March 22 interview; see footnote 3, Document 156.
3. Nixon underlined the first half of this sentence.
4. Nixon underlined this sentence and wrote, “Sporadic attacks,” in the left margin.
5. Nixon highlighted this sentence.
6. Attached but not printed is an undated paper entitled “Assumptions and Quantitative Estimate for Assessing the Effects of Lam Son.”