The domino theory existed from the 1950s to the 1980s. It was promoted at times by the United States government, and speculated that if one state 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.
Finally, you have broader considerations that might follow what you would call the "falling domino" principle. You have a row of dominoes set up, you knock over the first one, and what will happen to the last one is the certainty that it will go over very quickly. So you could have a beginning of a disintegration that would have the most profound influences.
In 1945, the Soviet Union brought most of the countries of Eastern Europe and Central Europe under its influence as part of the post-World War II settlement, prompting Winston Churchill to declare in a speech in 1946 at Westminster College in Fulton, Missouri that:
|“||From Stettin in the Baltic to Trieste in the Adriatic an "iron curtain" has descended across the Continent. Behind that line lie all the capitals of the ancient states of Central and Eastern Europe. Warsaw, Prague, Budapest, Belgrade, Bucharest and Sofia; all these famous cities and the populations around them lie in what I must call the Soviet sphere, and all are subject, in one form or another, not only to Soviet influence but to a very high and in some cases increasing measure of control from Moscow.||”|
Following the Iran crisis of 1946, Harry Truman declared what became known as the Truman Doctrine in 1947, promising to contribute financial aid to Greece during the Civil War and to Turkey following World War II, in the hope that this would impede the advancement of Communism into Western Europe. Later that year, diplomat George Kennan wrote an article in Foreign Affairs magazine that became known as the "X Article", which first articulated the policy of containment, arguing that the further spread of Communism to countries outside a "buffer zone" around the USSR, even if it happened via democratic elections, was unacceptable and a threat to U.S. national security. Kennan was also involved, along with others in the Truman administration, in creating the Marshall Plan, which also began in 1947, to give aid to the countries of Western Europe (along with Greece and Turkey), in large part with the hope of keeping them from falling under Soviet domination.
In 1949, China became a Communist country (officially the People's Republic of China) after Chinese Communist rebels defeated the Nationalist Republican government in the conclusion of the Chinese Civil War (1927~1949). Two Chinas were formed - mainland 'Communist China' (People's Republic of China) and 'Nationalist China' Taiwan (Republic of China). The takeover by Communists of the world's most populous nation was seen in the West as a great strategic loss, prompting the popular question at the time, "Who lost China?"
Korea had also partially fallen under Soviet domination at the end of World War II, and in 1950 fighting broke out between Communists and Republicans that soon involved troops from China (on the Communists' side), and the United States and 15 allied countries (on the Republicans' side). The war has not officially ended to this day but the fighting ended in 1953 with an armistice that left Korea divided into two nations, North Korea and South Korea.
In March 1954, the Viet Minh, a Communist and nationalist army, defeated French troops and took control of what became North Vietnam. This caused the French to fully withdraw from the region then known as French Indochina, a process they had begun earlier. The region now comprised four independent countries: North Vietnam, South Vietnam, Cambodia and Laos.
President Eisenhower was the first to refer to countries in danger of Communist takeover as dominoes, in response to a journalist's question about Indochina in an April 7, 1954 news conference, though he did not use the term "domino theory". If Communists succeeded in taking over the rest of Indochina, Eisenhower argued, local groups would then have the encouragement, material support and momentum to take over Burma, Thailand, Malaya and Indonesia; all of these countries had large popular Communist movements and insurgencies within their borders at the time.
This would give them a geographical and economic strategic advantage, and it would make Japan, Taiwan, the Philippines, Australia, and New Zealand the front-line defensive states. The loss of regions traditionally within the vital regional trading area of countries like Japan would encourage the front-line countries to compromise politically with communism.
Eisenhower's domino theory of 1954 was a specific description of the situation and conditions within Southeast Asia at the time, and he did not suggest a generalized domino theory as others did afterward.
The John F. Kennedy administration intervened in Vietnam in the early 1960s to, among other reasons, keep the South Vietnamese "domino" from falling. When Kennedy came to power there was concern that the communist-led Pathet Lao in Laos would provide the Viet Cong with bases, and that eventually they could take over Laos.
Arguments in favor of the domino theory 
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The primary evidence for the domino theory is the spread of communist rule in three Southeast Asian countries in 1975, following the communist takeover of Vietnam: South Vietnam (by the Viet Cong), Laos (by the Pathet Lao), and Cambodia (by the Khmer Rouge). It can further be argued that before they finished taking Vietnam prior to the 1950s, the communist campaigns did not succeed in Southeast Asia. Note the Malayan Emergency, the Huk Rebellion in the Philippines, and the increasing involvement with Communists by Sukarno of Indonesia from the late 1950s until he was deposed in 1965. All of these were unsuccessful Communist attempts to take over Southeast Asian countries which stalled when communist forces were still focused in Vietnam.
Walt Rostow and Lee Kuan Yew have argued that the U.S. intervention in Indochina, by giving the nations of ASEAN time to consolidate and engage in economic growth, prevented a wider domino effect. McGeorge Bundy argues that the prospects for a domino effect, though high in the 1950s and early 1960s, were weakened in 1965 when the Indonesian communist party was destroyed. However, proponents ultimately believe that the efforts during the containment (i.e. Domino Theory) period, ultimately led the demise of the Soviet Union and the end of the Cold War.
Some supporters of the domino theory note the history of communist governments supplying aid to communist revolutionaries in neighboring countries. For instance, China supplied the Vietminh, the North Vietnamese army, with troops and supplies, and the Soviet Union supplied them with tanks and heavy weapons. The fact that the Pathet Lao and Khmer Rouge were both originally part of the Vietminh, not to mention Hanoi's support for both in conjunction with the Viet Cong, also give credence to the theory. The Soviet Union also heavily supplied Sukarno with military supplies and advisors from the time of the Guided Democracy in Indonesia, especially during and after the 1958 civil war in Sumatra.
Noam Chomsky, a linguist, writes that he believes the Domino theory is roughly accurate, although he put a more positive spin on the threat, writing on the basis that economic improvements to a poor country will always bring better life for its people. If a people in a poor country see another poor country dictate its economy and improve it, the former will of course want to emulate the latter. This is why, he claims, the US put so much effort into suppressing so-called "people's movements" in Chile, Vietnam, Nicaragua, Laos, Grenada, El Salvador, Guatemala, etc. "The weaker and poorer a country is, the more dangerous it is as an example. If a tiny, poor country like Grenada can succeed in bringing about a better life for its people, some other place that has more resources will ask, 'Why not us?'" Chomsky refers to this as the "threat of a good example." Chomsky claims there are two domino effects, one internally discussed between US policy makers, which is that of the "Good Example", and another for public consumption, that of the spread of Communism.
Arguments against the domino theory 
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The primary evidence against the domino theory is the failure of Communism to take hold in Thailand, Indonesia, and other large Southeast Asian countries after the end of the Vietnam War, as Eisenhower's speech warned it could. However, proponents of this policy argue that this was due in part to the effects of both the Korean and Vietnam Wars.
Critics of the theory charged that the Indochinese wars were largely indigenous or nationalist in nature (such as the Vietnamese driving out the French), and that no such monolithic force as "world communism" existed. There was already fracturing of communist states at the time, the most serious of which was the rivalry between the Soviet Union and China, known as the Sino-Soviet split, which began in the 1950s.
Indeed, Vietnam and Cambodia were at odds from the very beginning. Rivalry between China and the USSR may have exacerbated tensions between them, since Vietnam had affiliated itself with the USSR and Cambodia with China, but nationalism and territorial disputes were obviously more significant factors. Border conflicts, mostly in the form of massacres of Vietnamese peasants carried out by the Khmer Rouge, occurred frequently for the duration of their nearly four years in power, eventually leading to the Cambodian-Vietnamese War of 1978-1979, when Vietnam overthrew the Khmer Rouge and took control of Cambodia. This in turn led China to attack Vietnam in 1979 in the brief Sino-Vietnamese War, and to U.S. and Thai support for the Khmer Rouge, who renounced communism and continued to fight as a guerrilla force against the Vietnamese-backed government until the mid-1990s.
In the cases of both Laos and Cambodia, the adoption of communism was directly attributable to the Vietnam War, which had spread over the borders of Vietnam into these countries, and to Vietnam's political regional ambitions, which included directly organizing communist parties in both countries. The fall of Laos was essentially due to repeated outright invasions by Vietnam and the inability of the army of Laos to defend the country. The fall of Cambodia had more complex causes but ultimately also resulted from the country being dragged into the Vietnam war, first by the Viet Cong who operated bases in the country and used it as part of the Ho Chi Minh trail, and then by full scale NVA attack, in conjunction with the Khmer Rouge, against the pro-U.S Lon Nol republic. The U.S. and South Vietnamese forces also contributed to widening of the war when they invaded and heavily bombed Cambodia in an attempt to root out those bases, causing an upsurge of popular resentment Opponents also argued that the domino theory misrepresented the real nature of the widespread and growing civil opposition that the previous, U.S.-backed regimes in these countries had generated because of entrenched official corruption and widespread human rights abuses, notably in South Vietnam.
Applications to communism outside Southeast Asia 
Michael Lind has argued that though the domino theory failed regionally, there was a global wave, as communist or Marxist-Leninist regimes came to power in Benin, Ethiopia, Guinea-Bissau, Madagascar, Cape Verde, Mozambique, Angola, Afghanistan, Grenada, and Nicaragua during the 1970s. The global interpretation of the domino effect relies heavily upon the "prestige" interpretation of the theory, meaning that the success of Communist revolutions in some countries, though it did not provide material support to revolutionary forces in other countries, did contribute morale and rhetorical support.
In this vein, Argentine revolutionary Che Guevara wrote an essay, the "Message to the Tricontinental", in 1967, calling for "two, three ... many Vietnams" across the world. Historian Max Boot wrote, "In the late 1970s, America's enemies seized power in countries from Mozambique to Iran to Nicaragua. American hostages were seized aboard the SS Mayaguez (off Cambodia) and in Tehran. The Red Army invaded Afghanistan. There is no obvious connection with the Vietnam War, but there is little doubt that the defeat of a superpower encouraged our enemies to undertake acts of aggression that they might otherwise have shied away from."
In addition, this theory can be further bolstered by the rise in terrorist incidents by left-wing terrorist groups in Western Europe, funded in part by Communist governments, between the 1960s and 1980s. In Italy, this includes the kidnapping and assassination of former Italian Prime Minister Aldo Moro, and the kidnapping of former US Brigadier General James L. Dozier, by the Red Brigades.
In West Germany, this includes the terrorist actions of the Red Army Faction. In the far east the Japanese Red Army carried out similar acts. All four, as well as others worked with various Arab and Palestinian terrorists, which like the red brigades were backed by the Soviet Bloc.
In the 1977 Frost/Nixon interviews, Richard Nixon defended America's destabilization of the Salvador Allende regime in Chile on domino theory grounds. Borrowing a metaphor he had heard, he stated that a Communist Chile and Cuba would create a "red sandwich" that could entrap Latin America between them. In the 1980s, the domino theory was used again to justify the Reagan administration's interventions in Central America and the Caribbean region.
In his memoirs, former Rhodesian Prime Minister Ian Smith described the successive rise of authoritarian left-wing governments in Sub-Saharan Africa during decolonization as "the communists' domino tactic". The establishment of pro-communist governments in Tanzania (1961–64) and Zambia (1964) and explicitly Marxist-Leninist governments in Angola (1975), Mozambique (1975), and eventually Rhodesia itself (in 1980) are cited by Smith as evidence of "the insidious encroachment of Soviet imperialism down the continent."
Other applications 
Some foreign policy analysts in the United States have referred to the potential spread of both Islamic theocracy and liberal democracy in the Middle East as two different possibilities for a domino theory. During the Iran-Iraq war the United States and other western nations supported Iraq, fearing the spread of Iran's radical theocracy throughout the region. In the 2003 invasion of Iraq, some neoconservatives argued that when a democratic government is implemented, it would then help spread democracy and liberalism across the Middle East, and a war can install a democratic government. This has often been referred to as a "reverse domino theory," to avoid confusion with the communist domino theory because it's based on influence instead of military aid.
See also 
Domino effect 
- Rogue Regimes: Terrorism and Proliferation, pg. 230, Raymond Tanter, Macmillan, 1999
- President Eisenhower’s Press Conference of April 7, 1954
- "The Threat of a Good Example", Noam Chomsky
- "Rough Draft of History: 'All Right, Let's Get the @#!*% Out of Here'", Richard Gott, August 11, 2005
- "Another Vietnam?", Max Boot, The Wall Street Journal, August 24, 2007
- KGB Active Measures
- Red Army Faction
- Brigate Rosse
- The Last Years of the Monroe Doctrine, 1945-1993, p. 133 Gaddis Smith
- Smith, Ian (2008). Bitter Harvest: Zimbabwe and the Aftermath of Its Independence. London: John Blake Publishing. p. 280. ISBN 978-1-84358-548-0.
- Smith 2008: 147
- Smith 2008: 183
- "The War and the Peace", Robert Wright, Slate, April 1, 2003