Khrushchev solidified the concept in Soviet foreign policy in 1956 at the 20th Congress of the Communist Party of the Soviet Union. The policy arose as a temptation to reduce hostility between the two superpowers, particularly in light of the possibility of nuclear war. The Soviet theory of peaceful coexistence asserted that the United States and USSR, and their respective political ideologies, could coexist rather than fighting one another, and Khrushchev tried to demonstrate his commitment to peaceful coexistence by attending international peace conferences, such as the Geneva Summit, and by traveling internationally, such as his 13-day trip to tour the United States in 1959. The World Peace Council founded in 1949 and largely funded by the Soviet Union attempted to organize a peace movement in favor of the concept internationally.