What led the us and their allies to get involved the vietnam war

Concerns about Communism spreading if Vietnam went communist, this was known as Domino Theory. U.S. foreign policy was shaped by Anti-communist views.

The  United States and its allies worried that if Vietnam fell to the communists, other countries in Southeast Asia would follow.  This was known as "domino theory" -- that the spread of communism in Vietnam would result in other countries in the region falling like dominoes to the influence of communism.  

President Dwight Eisenhower is the one who initiated the use of the term "domino theory."  In a speech he gave in April, 1954, Eisenhower warned that if French Indochina fell to communism, it very likely could cause a domino  effect in Southeast Asia.  French Indochina is what the region of Vietnam was called during the days of French colonialism there.  The movement against French colonial control was led by Vietnamese nationalist who also happened to be communists.  The Vietamese nationalist / communist movement was led by HoChi Minh.

the hollywood film industry of 1950 was threatened on several different fronts. television broadcasting was rapidly becoming the dominant entertainment medium in the united states. the paramount anti-trust consent decree requiring separate ownership for production companies and theater chains had gone into effect on 1 january 1950. large numbers of young men and women were marrying, having children, and moving to the suburbs, which affected the viability of downtown first-run movie theaters. foreign revenues were endangered by protectionist tactics including quota systems, high taxes, and blocked funds. finally, the morality and patriotism of hollywood films and filmmakers were under attack from government, religious, and citizens' groups.

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