165. Telegram From the Commander in Chief, Military Assistance Command, Vietnam (Westmoreland) to the Commander in Chief, Pacific (Sharp)1

43199. Subject: Cross Border Combat Operations—Cambodia.

Based on DIA Intelligence Studies, our experience during operation Silver Bayonet, and our observations and intelligence, it is perfectly clear to us that the border areas of Cambodia now contain motorable infiltration routes, command centers, base, training and supply areas along the pattern of the long development of a similar nature in Laos.2
The buildup in Laos started in the late 1950s and owing to the skill of the North Vietnamese in hiding their activities, their ability to control completely this corridor area and restrictions against intelligence collection, it has only been recently that the full scope of their effort has become apparent. We now have arrived at a point where entire divisions are being infiltrated through this corridor.
Now that we are confronted with a similar situation in Cambodia, we must face up to the facts of life and recognize that we face a major threat and that we will not be able to produce the kind of evidence which would stand up in court against those who insist on such proof! Although to us it is painfully clear and quite obvious what has happened; Sihanouk does not control his border area any more than Souvanna Phouma controls his. Furthermore, there is nothing Sihanouk can do about it even if he desired to do so, which is highly doubtful. Therefore, it is in our national interest to draw the obvious conclusion and take what measures are necessary to reduce the utility of this area to the PAVN/VC and to mount offensive air attacks against them as necessary.
We are now in a target development phase in this area in connection with B–52 strikes.
We intend to resume offensive operations in the border areas of Pleiku, Kontum and Darlac in late December, January and February.
In order to foresee and forestall the problems which stem from the use of a Cambodian sanctuary, request the following authorities be granted as standard operating procedures whenever US troops operate [Page 367] in areas adjacent to the Cambodian border in Darlac, Pleiku and Kontum provinces.
Artillery and air strikes may be made against enemy weapons firing from the Cambodian side of the border against US troops. This authority would not exceed light artillery range of 10 kilometers into Cambodia.
Ground troops engaged with an enemy on or near the border may maneuver into Cambodia up to two kilometers if such maneuver is necessary for the preservation of the force or the attainment of the objective within South Vietnam.
Observation aircraft and airborne FACʼs in support of US operations may fly reconnaissance and surveillance missions within a 10 kilometer strip on the Cambodian side of the border. They may direct air and artillery strikes from in-country resources against enemy forces and installations positively identified by group reconnaissance elements and against enemy forces when their movements or actions clearly indicate they are hostile.
Specially trained ground reconnaissance elements may operate to a depth of 5 kilometers on the Cambodian side of the border. These specially trained reconnaissance elements may be composed of a mixture of US and Vietnamese or CIDG Montagnard personnel as required. Infiltration may be on foot or by helicopter and extraction will be in the same manner.
No Cambodians will be engaged except in self-defense nor will any Cambodian village be attacked with air, artillery fire or ground forces.
These authorities have been requested only because they are necessary in connection with the defense of South Vietnam. They do not indicate that we seek a wider war nor will they be so applied.
The US Ambassador concurs with this message and adds the following comment: “I approve the proposed action. But I believe we should be clear in our own minds that we are taking it as an integral part of our effort for the defense of South Vietnam and not because we seek a wider war. Whereas and if the time comes to discuss these matters publicly, it will be well to have this self-limiting statement as a part of the record.”
  1. Source: Department of State, Central Files, POL 32–1 CAMB–LAOS. Top Secret. Also sent to JCS and Department of State, which is the source text.
  2. In telegram 1622 to Saigon, December 10, the Department of State stated that while it was also concerned about Viet Cong use of Cambodian territory as limited safe havens and logistical bases, it noted that there were extensive intelligence gaps on the issue. It asked for additional intelligence to bolster Westmorelandʼs assertion of widespread VC use of Cambodia. (Ibid., POL 27 VIET S) Joint Embassy/MACV telegram 2149 from Saigon, December 15, contains a synopsis of selected intelligence on VC use of Cambodia. (Ibid.)