Peaceful coexistence was a theory developed and applied by the Soviet Union at various points during the Cold War in the context of primarily Marxist–Leninist foreign policy and was adopted by Soviet-influenced "Socialist states" that they could peacefully coexist with the capitalist bloc (i.e., non-socialist states). This was in contrast to the antagonistic contradiction principle that Communism and capitalism could never coexist in peace. The Soviet Union applied it to relations between the western world, particularly between the United States and NATO countries and the nations of the Warsaw Pact.