The promotion of Mikhail Gorbachev to General Secretary in 1985 and his 'new thinking' on foreign and domestic policy was likely an important factor in the Soviets' decision to withdraw. Gorbachev had been attempting to remove the Soviet Union from the economic stagnation that had set in under the leadership of Brezhnev, and to reform the Soviet Union's economy and image with the Glasnost and Perestroika policies. Gorbachev had also been attempting to ease cold war tensions by signing the Intermediate-Range Nuclear Forces Treaty with the U.S. in 1987 and withdrawing the troops from Afghanistan, whose presence had garnered so much international condemnation. Gorbachev regarded confrontation with China and resulting military build ups on that border as one of Brezhnev's biggest mistakes. Beijing had stipulated that a normalization of relations would have to wait until Moscow withdrew its army from Afghanistan (among other things), and in 1989 the first Sino-Soviet summit in 30 years took place. At the same time, Gorbachev pressured his Cuban allies in Angola to scale down activities and withdraw even though Soviet allies were faring somewhat better there. The Soviets also pulled many of their troops out of Mongolia in 1987, where they were also having a far easier time than in Afghanistan, and restrained the Vietnamese invasion of Kampuchea to the point of an all out withdrawal in 1988. This massive withdrawal of Soviet forces from such highly contested areas shows that the Soviet government's decision to leave Afghanistan was based upon a general change in Soviet foreign policy – from one of confrontation to avoidance of conflict wherever possible.