Cold War (1985–1991) reduced some strategic arms unilaterally. Fundamental to the dissolution of the Soviet Union, the Gorbachev policy initiatives of Restructuring ("Perestroika") and Openness ("Glasnost") had ripple effects throughout the Soviet world, including eventually making it impossible to reassert central control over Warsaw Pact member states without resorting to military force. On June 12, 1987, Reagan challenged Gorbachev to go further with his reforms and democratization by tearing down the Berlin Wall. In a speech at the Brandenburg Gate next to the wall, Reagan stated: While the aging communist European leaders kept their states in the grip of "normalization", Gorbachev's reformist policies
Mikhail Gorbachev carried out only personnel shifts rather than structural change. Andropov encouraged Gorbachev to expand into policy areas other than agriculture, preparing him for future higher office. With Andropov's encouragement, Gorbachev sometimes chaired Politburo meetings. In April 1983, Gorbachev delivered the annual Lenin's birthday speech; this required him re-reading many of Lenin's later writings, in which the first Soviet leader had called for reform, and encouraged Gorbachev's own conviction that reform was needed. In May 1983, Gorbachev was sent to Canada, where he met Prime Minister Pierre Trudeau and spoke to the Canadian parliament. There, he met and befriended the Soviet