U.S. President Dwight D. Eisenhower described the domino theory during an April 1954, news conference, when referring to communism in Indochina.

The geopolitical theory stated that if one country fell to a communist takeover, the surrounding countries would fall like a collapsing row of dominoes.

 The domino theory was used by successive United States administrations during the Cold War to justify the need for American intervention around the world.

Source: Wikipedia