What happened in the Soviet Union and other East European socialist countries?

Major factors in the serious setbacks to socialism include: the constant attacks by capitalist countries, which went from economic harassment through political subversion up to military intervention and the threat of military occupation; the stresses put on socialist economies by the arms race and military threats and attacks; the fortress mentality which developed in those countries as a result of the constant attacks, leading to inadequate development of socialist democracy; insufficient adoption of the advances of the scientific-technological revolution; economic models which didn’t give sufficient weight to constantly revolutionizing the means of production; the historical circumstances of socialism starting in what were primarily peasant societies; bureaucratization in the state apparatus of those countries; a serious blurring of important lines between the Party and the state and between accomplishing objectives by administrative means and by political means; and a formal approach to Marxist ideological and educational work rather than a truly dynamic, dialectical approach.