161. Telegram From the Department of State to the Embassy in Vietnam1

1399. State/Defense message. With reference to your unnumbered message concerning authorization for certain operations in Laos and Cambodia:2

Intensified air campaign in Laos appears to us desirable but less urgent than question of immediate operations into Cambodia. In view of recent agreements re Steel Tiger3 between MACV and Embassy Vientiane, not clear that additional authorization needed. If you consider present arrangements inadequate, let us know.
We concur in tactical air and B–52 strikes along Cambodian/SVN border up to border itself. These may be authorized in the field of tactical operations and in accordance with existing procedures for B–52 strikes.
We further believe that both GVN and US forces must have all authority necessary for self-defense. We also recognize that present [Page 357] engagement is special case involving major PAVN/VC units who have been re-grouping and attacking again throughout Pleiku area since engagement began. While doctrine of hot pursuit can be strongly supported by analogy, there is no possible doubt on justification of self-defense.
Accordingly, separate message through military channels4 will contain authorization for self-defense measures applicable to existing Silver Bayonet5 situation. This will include authority to US/GVN units to return fire, to eliminate fire coming from Cambodia, and to maneuver into Cambodian territory as necessary to defend selves while actively engaged in contact with PAVN/VC units. This authority includes artillery and close air support operations against enemy units as long as such units are actually engaged with US or GVN forces. It excludes authority to engage Cambodian forces, if encountered, except in self-defense, to conduct tactical air or artillery operations against populated Cambodian areas, or to attack Cambodian base areas other than in circumstances where justification of self-defense exists in terms of continuing engagement and direct threat to GVN or US forces. We recognize these distinctions might be most difficult to preserve, but from political standpoint it is essential that this be done.
The foregoing discussion has direct bearing on handling of any press announcements of operations. This will require careful advance preparation by the Embassy and MACV with following guidelines in mind:
While location of action should not be stated incorrectly, we should avoid as long as possible any express statement that GVN and US forces have been in Cambodia. This might involve stating that exact locations being checked further. Obviously, we would be forced to eventual admission, but point should be got across that border terrain difficult and boundary lines hard to check completely against reported positions. (We do not here understand that border in this area is disputed, so that this rationale should not be advanced unless we have very solid evidence to support it.)
Stress should be placed on theme that GVN and/or US forces were under attack and that measures taken were in self-defense. Term “self-defense” should be driven home, and terms such as “immediate pursuit” or “hot pursuit” should not be used.
Spokesman should not be drawn into legal basis and justification for action taken. Tentatively, we would probably prefer to handle this here, but in any case justification might depend heavily on circumstances, [Page 358] whether we argued in terms of terrain and border difficulty or frankly admitted Cambodian territory involved and went on to justification in terms of self-defense. We also need to think further, and are doing so urgently, on just how we frame our justification in terms of Sihanoukʼs reaction. This could depend heavily on evidence obtained form prisoners or during action itself that tended to negate his assertion, repeated only this week, that Cambodian territory has never been used even as a sanctuary. Evidence of physical installations would of course be particularly useful, and in general we would like to have a special report from you or MACV tomorrow on this subject as it stands now, and the same on a continuing basis particularly if border actually crossed.
Question of Washington authority should be met solely by statement that Washington had given general authorization for forces to take actions necessary for their self-defense. Exact terms of authority should under no circumstances be discussed.

We believe above covers your immediate need and urgent problems which might arise if authority were used. Please keep us advised, if necessary on flash basis. Exdis heading will be sufficient for messages in this channel if sensitive, and of course military operation reports should come on regular channel with appropriate limits or distribution.

  1. Source: Department of State, Central Files, POL 27 VIET S. Top Secret; Immediate. Drafted by William Bundy, cleared by McNamara, Wheeler, and McGeorge Bundy, and approved by Ball. Repeated to Rio de Janeiro for Secretary Rusk only.
  2. See footnote 2, Document 160.
  3. Steel Tiger was the code name for U.S. Air Force and Navy air interdiction of the Ho Chi Minh Trail in Laos.
  4. Not further identified.
  5. Silver Bayonet was the code name for US–GVN military operations in Plei Ku Province of South Vietnam.