Oh that...

And while the theory was never really "disproven",

"Domino Theory" worked in Eastern Europe and Korea.

and it also often ignores other factors like living standarts in said countries and the remains of colonialism during that time, the overall estimated effect after the Vietnam War never came to be so its more safe to say it was more a oversimplification of the whole process than anything that was mostly used as War propaganda.

"Domino Theory" might or might not have worked in Vietnam. The wild cards were 1. Long history of conflict between Vietnam and China. 2. Heavy Chinese presence in Vietnam even before Communist Mao Zedong took over Kuomingtang's Chang-kai Shek's task of Sino-colonization of Vietnam in early 1950's.

/r/facepalm Thread Parent Link - i.imgur.com