The Cold War was a state of relations between opposing states or social systems with a constant policy of reciprocated hostility that, nonetheless, was not allowed to escalate to the level of military force. Triangular politics was to become a distinctive feature of the Cold War in the 1970s. The two faces of the Cold War existed alongside each other because of the increased costs of the use of force. Stalin's political strategy combined opportunistic probing with caution about provoking a military reaction. In his major public address to the Twentieth Congress, Khrushchev proclaimed the major tasks of Soviet foreign policy: strengthening the USSR's defense potential and exposing the activities of the enemies of peace. In 1960 Sino-Soviet differences resurfaced, with the publication by the Chinese of a lengthy critique of the Russians under the title 'Long Live Leninism'. The end of the Cold War actually seemed to have an adverse impact on the Third World.