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SA-2s in Laos. Hanoi could attempt to use Migs if other measures to foil or
 breach the system failed, but we think this is least likely. The Communists
 might attempt to harass the control center in northeast Thailand.

15. Thwarting and Breaching the System. For some time, Hanoi would continue
 to move forces through the Sensor zone, accepting the risk of losses and
 delays, until the effectiveness of the system was thoroughly tested. Hanoi would
 try to sweep some of the sensors and mines, and develop an ever shifting and
 expanding maze of concealed trails. The Communists would depend on the
 burgceoning number of trails and on unpredictable use patterns to complicate
 the US efforts to replace sensors and mines. They would probably also move
 in smaller groups, widely separated and at night, and to the extent possible
 concentrate infiltration in times of bad weather. The anti-inflitration belt through
 which they would have to pass is about 12 miles deep, and 35 to 40 miles wide.
 Thus, infiltrating troops could be dispersed so that they would present only low
 density targets.

16. Eventually, the Communists would probably also resort to a variety of
 noisemaking devices including rifles, mortars, and artillery, to activate the
 acoustic sensors and to call in US strike aircraft on false alarms. With Chinese
 or Soviet help they might in time develop several effective jamming techniques.
 Because the acoustic sensors near the foot-trail system are triggered by the noise
 of the button, bomblets when stepped on, the Communists would probably devote
 some effort to making trails clear and hard-packed, so that button bomblets
 would be easily visible and avoidable. They would also take additional steps
 to camouflage such trails.

17. Alternatives. Should Hanoi's efforts to breach the antipersonnel sector
 turn out to be ineffective or too costly, it could develop infiltration trails further
 west, as far as the Mekong River if necessary, although probably not into Thailand.
 This would not be easy, for the present system has been long established,
 has experienced local guides, supply depots geared to both the trails and road
 system, and farms along the route which supply some of the food consumed
 by the infiltrators. To duplicate this system would be a major undertaking, and
 would require clearing the area of Lao army troops, thus widening the ground
 war in Laos.

18. We think it quite unlikely that the Communists would use the Se Bang
 Hieng tributaries, the only streams in the area, for the movement of personnel.
 Hanoi would probably not rely on its helicopters to move troops over the anti-infiltration
 system. The route by sea is not feasible for large-scale infiltration
 of personnel because of Operation Market Time. We think that for political
 reasons Cambodian ports and routes could not be used by the Communists for
 the infiltration of any significant number of personnel.

19. In sum, we think the major effort would be devoted to breaching the anti-
 personnel sector rather than going around it. This might require some increase
 in total Communist forces deployed in the infiltration zones, in order to work
 against they system and provide greater protection from air strikes.

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TS 0039350

COPY LBJ LIBRARY