The domino theory was a common policy during the Cold War period, as the theory assumed that the existence of a communist government in a country would in turn lead to the control of the communist regime over the neighboring country.

Where each of them falls in succession as a row of harmonious domino stones, and the United States used that theory in Southeast Asia to justify its involvement in the Vietnam War and support the non-communist dictator in it, but the American failure was much less and the domino theory did not bear any success and failed in the spread of communism in Southeast Asia.

The Vietnamese national leader (Hu Xi) declared the independence of Vietnam from French control in 1945 A.D. and the war began that put the communist regime under the leadership of Hu Xi in confrontation with France in South Vietnam, that is, North Vietnam's confrontation with the South, and during the era of Harry Truman's administration the US government provided financial and military aid In secret to France, where the prevailing justification was that the success of communism in Indochina would make communism spread in Southeast Asia, and using the same logic, Harry provided aid to Greece and Turkey to contain communism.

With the advent of 1950 AD, the idea of ​​the American foreign policy's conviction increased in the idea that the fall of India under the umbrella of the communist regime would lead to the collapse of neighboring countries in Southeast Asia, and the Security Council included the theory on India in its council held in 1952 AD and in 1954 AD during the Battle of Din Bayan between Vietnam. North and France, US President Eisenhower described the situation as falling dominoes, as his view was that the fall of North Vietnam into the communist grip would lead to similar victories in all neighboring countries.

After the end of the Geneva conference, which ended the ongoing war between North Vietnam and the French forces, and Vietnam was separated at the 17th parallel, then the United States led the organization of the Seato Treaty, which is the alliance that obliges countries to take any measures against security threats, and Kennedy, Eisenhower's successor, pledged to support Vietnamese President Ngo Dinh Diem in South Vietnam and the consolidation of non-communist forces that will lead a civil war in Laos between 1961 AD - 1962 AD, and after the internal opposition to President Diem in 1963 AD, Kennedy retreated from his support and reaffirmed the importance of the domino theory.

Diem was killed, and three weeks after he was killed, a military coup occurred against him, Kennedy was assassinated, and his successor Johnson continued to support the theory, the military situation was escalated in Vietnam, and American soldiers were sent to war, and the theory became disintegrated after it failed to seize the nature of the Vietnamese conflict and the failure of American political makers to assume Hu Shi is nothing but a puppet of the leaders of the communist regimes in Russia and China.

In the end, all American efforts to control communism failed, and North Vietnamese forces entered Saigon in 1975 CE. Communist regimes did not spread to the rest of the continent except for Cambodia, but the rest of the region remained outside communist control and the theory failed to assume it.