The Domino Theory of international relations was first outlined by United States President Dwight D. Eisenhower at a press conference on April 7, 1954.
President Dwight D. Eisenhower
The theory held that if one country or state in a particular region of the world came under the influence of communism, then surrounding and nearby countries would fall in a domino effect. The theory was often held up as justification for United States intervention in Vietnam.