Nor would surrender in Viet-Nam bring peace, because we learned from Hitler at Munich that success only feeds the appetite of aggression. The battle would be renewed in one country and then another country, bringing with it perhaps even larger and crueler conflict, as we have learned from the lessons of history.

Lyndon B. Johnson (1908-1973) American politician, educator, US President (1963-69)

Speech (1965-07-28), News Conference, White House, Washington, D. C.
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The pre-conference prepared remarks were the first definitive set of national policy statements as to America's growing military presence in Viet Nam. The idea that a Communist victory in Viet Nam would lead to similar wars in other nations was called the "Domino Theory."