Kennedy's foreign policy was dominated by American confrontations with the Soviet Union, manifested by proxy contests in the global state of tension known as the Cold War. Like his predecessors, Kennedy adopted the policy of containment, which sought to stop the spread of Communism. President Eisenhower's New Look policy had emphasized the use of nuclear weapons to deter the threat of Soviet aggression. Fearful of the possibility of a global nuclear war, Kennedy implemented a new strategy known as flexible response. This strategy relied on conventional arms to achieve limited goals. As part of this policy, Kennedy expanded the United States special operations forces, elite military units that could fight unconventionally in various conflicts. Kennedy hoped that the flexible response strategy would allow the U.S. to counter Soviet influence without resorting to war. At the same time, he ordered a massive build-up of the nuclear arsenal to establish superiority over the Soviet Union.