<P> The United States had an anti-colonial and anti-communist stance in its foreign policy throughout the Cold War . Military forces from the United States and the United Kingdom were heavily involved in the Korean War, fighting under a United Nations mandate . Military forces withdrew when a stalemate was implemented in 1953 . When the Suez Crisis erupted in October 1956, the United States feared a wider war, after the Soviet Union threatened to intervene on the Egyptian side . Thus the United States applied sustained econo - financial pressure to encourage and ultimately force the United Kingdom, Israel and France to end their invasion of Egypt . British post-war debt was so large that economic sanctions could have caused a devaluation of sterling . This was something the UK government intended to avoid at all costs, and when it became clear that the international sanctions were serious, the British and their French allies withdrew their forces back to pre-war positions . The following year saw the resignation of Sir Anthony Eden . </P> <P> Dwight D. Eisenhower's victory in the American presidential election in 1952 might have been expected to guarantee a continuance of good United States - United Kingdom relations, if not a period of even closer collaboration . Anglo - American cooperation during Eisenhower's presidency was troubled, approaching in 1956 a complete breakdown that represented the lowest point in the relations between the two countries since the 1920s . </P> <P> Through the US - UK Mutual Defence Agreement signed in 1958, the United States assisted the United Kingdom in their own development of a nuclear arsenal . In April 1963, John F. Kennedy and Harold Macmillan signed the Polaris Sales Agreement to the effect of the United States agreeing to supply the UGM - 27 Polaris ballistic missile to the United Kingdom for use in the Royal Navy's submarine fleet starting in 1968 . </P> <P> The United States gradually became involved in the Vietnam War in the early 1960s, but this time received no support from the United Kingdom . Anti-Americanism due to the Vietnam War and a lack of American support for France and the United Kingdom over the Suez Crisis weighed heavily on the minds of many in Europe . Harold Wilson refused to send British troops to Indochina . </P>

When did the us and great britain become allies