The Vietnam War was a major factor in the US shift towards a foreign policy of detente during the Cold War. The war was extremely unpopular in the United States, and it led to a great deal of public disillusionment with the government's foreign policy. The war also put a strain on the US economy, and it contributed to the rise of inflation. In addition, the war made the United States more vulnerable to attack from the Soviet Union, as it tied up a large number of US troops in Vietnam. As a result of these factors, the US government began to seek ways to reduce tensions with the Soviet Union, and this led to the policy of detente.