In Southeast Asia, the United States government used the domino theory to justify its support of a non-communist regime in South Vietnam against the communist government of North Vietnam, and ultimately its increasing involvement in the long-running Vietnam War (1954-75).
The number of voting representatives in the House is fixed by law at no more than 435, proportionally representing the population of the 50 states.
The House of Representatives is composed of 480 members, of whom 300 are elected from the single-seat constituencies and 180 by the proportional representation system in which the nation is divided into 11 electoral blocs which according to size return between 6 and 30 members.