Final answer:
The Domino Theory led to the United States' significant intervention in Southeast Asia, particularly in Vietnam, to prevent the spread of communism. It influenced the US policy of containment and resulted in the provision of military and financial support to South Vietnam and other countries in the region.
Step-by-step explanation:
The Domino Theory was instrumental in shaping US foreign policy during the Cold War, particularly under President Dwight D. Eisenhower. This theory posited that if one country in a region came under the influence of communism, the surrounding countries would follow in a domino effect. Thus, the United States believed it was imperative to contain communism's spread to prevent its dominance globally. After the French defeat at Dien Bien Phu and their subsequent withdrawal, the US began sending military advisers to South Vietnam.
Eisenhower's policy of containment, influenced by the threats perceived from the Soviet Union and China, extended to decisions regarding military support and intervention in Southeast Asia. The US provided substantial aid to France during the Indochina War, and after the French exit, increasingly supported the South Vietnamese government to prevent what was seen as an inevitable communist takeover.
The feared cascade of communist takeovers in Southeast Asia and the broader implications for global democracy led to significant military and financial support from the US to South Vietnam and other nations such as Laos. Through a combination of military advisors, economic aid, and eventually, direct military intervention, the United States sought to maintain a balance of power and prevent communist ideology from gaining further ground as part of its broader Cold War strategy.