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ever, with some of the equipment which the system would employ (e.g., gravel
 mines), and would quickly identify the other types of mines employed. They
 would also soon realize the critical role of aircraft in the system. The sensors
 would probably be their greatest problem, not only because they would be difficult
 to locate, but because of their technical complexity and the number of different
 types. The North Vietnamese would probably seeks Soviet and Chinese
 Communist assistance in devising countermeasures.

11. The specific countermeasures the Communists might employ would vary
 depending on the sector involved, the effectiveness of each system, and the
 developing Communist experience with countermeasures. In general, their
 countermeasures are likely to fall into three basic categories: (a) measures designed
 to impede the installation and explotation of the system; (b) attempts to
 attack, thwart, or breach the system; and (c) attempts to use alternative routes,
 either within or outside of Laos.

B. The Physical Barrier

12. The Communists would probably regard the manned physical barrier as
 potentially the most effective part of the system. They would attempt to delay
 or prevent its construction by harassing work forces both from across the DMZ
 and from the rear. They are even now employing these tactics against the
 "Ky barrier." Once the barrier was installed, the Communists would probably
 attempt to achieve limited penetrations, but would probably not wish to risk
 high losses in order to breach it on a broad front. In any event, they would
 continue to harass the system. These actions would be taken with the hope of
 tying down large US forces in defensive positions.

C. The Antipersonnel Sector

13. The trail network to be covered by the central antipersonnel sector of
 the system is of great importance to the North Vietnamese. Due to the nature
 of the target, it has not been attacked extensively; the US has instead concentrated
 on the truck routes.

14. Defensive Measures. The Communists would probably recognize the key
 role of air support in the operation of the system and would probably make a
 major effort to increase their air defense in the area. Communist AAA fire in
 the Laotian Panhandle has shown a steady increase in the last year, although
 there does not appear to have been a significant increase in the number of AAA
 units. With continued supplies from China and the USSR, it is within Communist
 capabilities to augment substantially conventional AAA forces in the DMZ
 and Laos. The entire sector is well within the present zone of their GCI radar
 net. Depending on the location of the orbits of the aircraft which monitor the
 system, they might be vulnerable to Mig or SA-2 attack. The North Vietnamese
 already have some SA-2s in the vicinity of the DMZ and we think it likely they
 would increase the numbers of SA-2s there and deploy them nearer the northwest
 corner of the DMZ. It is also possible, but less likely, that they would deploy

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