You like to throw out Vietnam in posts, it seems you added our presence in Laos and Cambodia to your arguments in the last couple of days. In 1962 several nations including the US, USSR, China, and both N and S Vietnam signed a treaty in Geneva assuring the neutrality of Laos - no foreign troops, no pressure to form alliances, etc. N Vietnam had close to 10K troops in Laos; they never pulled them out - just simply denied their presence. Granted Laos was a mess - the neutralist faction waffled, the Pathet Lao still worked with communist counties, and there was a faction that we worked with as the problem increased. The Chinese had one of their infamous road building projects going in northern Laos. We and the French pulled our military per the treaty while N Vietnam with the knowledge of Russia and China simply denied they had troops there. Essentially they broke the treaty as it was being signed.