Domino theory Domino theory The domino theory was a theory prominent from the 1950s to the 1980s that posited that if one country in a region came under the influence of communism, then the surrounding countries would follow in a domino effect. The domino theory was used by successive United States administrations during the Cold War to justify the need for American intervention around the world. U.S. President Dwight D. Eisenhower described the theory during an April 7, 1954, news conference, when referring to communism in Indochina: In 1945, the Soviet Union brought most of the countries of eastern Europe and Central
US signals intelligence in the Cold War least in house arrest. A quote from "Life" magazine, generally considered friendly to Diem, suggested that a substantial number of non-communists had been arrested. This is followed by a brief note, "Yet in that same process of neutralizing opposition, Diem set the seeds for his own downfall." This followed by long redactions. Both Diem and the US Military Assistance Advisory Group (MAAG), according to the NSA history, felt the communists were going into "last gasps" in late 1959. US SIGINT support during the Vietnam War came principally from service cryptographic units, with some NSA coordination. Units still belonged to their