That started a war between Communist led Viet Minh regime in Hanoi and French backed regime in Saigon. The US provided the French army with military and financial assistance under President Harry S. Truman’s orders. The reasoning behind it was a communist victory in Indochina would result in communism spreading throughout in Europe and the Middle East more quickly.
In early 1950, US foreign policy had completely embraced the concept that the fall of Indochina to communism would result in the collapse of surrounding nations in Southeast Asia. In 1952 the National Security Council included the domino theory in its report on Indochina during the battle between Viet Minh and the French forces at Diem Bien Phu. Eisenhower anticipated as the "falling domino" principle. He viewed the loss of Vietnam to the communists would lead to communist victories in surrounding South east Asian countries, even as far as Australia and New