The disintegration of the Soviet Union resulted from a number of different factors. Three important ones are nationalism among Soviet satellite states, democratic opposition movements, and economic crisis. Along with these elements, the role of Mikhail Gorbachev should not be discounted. Although his attempt to reform communism was rejected, his reformist positions as Soviet premier helped open the way for full-fledged political dissidence. One of the major challenges faced by Europe in the wake of the collapse of communism has been that posed by ethnic nationalism, a problem that erupted violently in the Balkans in the 1990s. Immigration and the defense of human rights are two problems that now confront the United States, as well as a United Europe.