allow some limited operations by the North Vietnamese from
 bases in China, but under the tightest Chinese control so
 as to minimize the risks of US retaliation.
 28. Regardless of whether the North Vietnamese sought
 a sanctuary of some kind in China, there would be a continuing
 danger of air incidents near the Chinese border or over
 Chinese territory. On several occasions in recent weeks
 the Chinese have responded more vigorously to US air intrusion
 and to US strike aircraft flying over North Vietnam near the
 border. This seems likely to continue, as the nature of
 US air operations involves a chance of extending over Chinese
 territory. As for the USSR, we would not exclude the surfacing
 at some point of some Soviet military personnel in a "volunteer"
 role. In any case, increased Soviet and Chinese support would
 probably have the effect of reinforcing Hanoi's determination
 to persevere in its policies despite greater pressures on
 supply lines to China.
 29. Variant b. The most important additional effect of
 this variant would be the direct challenge it posed to the
 USSR. The Soviets might consider countering the interdiction
 by military actions in the area, or bringing pressures on the
 US or its allies in other areas (may Berlin). But these two
 courses seem too hazardous or unpromising. It is much more
 -15-
 
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