Since we now know Russian pilots flew against us in Korea, why wouldn’t they have done so in Vietnam?
They at least trained the North Vietnamese, who wanted nothing to do with Red China following 1,000 years of Chinese occupation.
Col. Broughton wasn’t the only Vietnam vet whose hatred of LBJ only grows as time goes on, if you get my drift.
IIRC from my reading of "Thud Ridge", he does relate seeing a uniquely painted Mig-21 come in on an intercept that he was sure was piloted by a Russian.