Based on completed author on the study of the Soviet-Afghan relations 1975-91gg. the article presents findings related to assess the adoption in December, 1979, the Soviet leadership decisions on the use of troops in Afghanistan. The analysis of the documents of the Politburo of the CPSU Central Committee and the existing points of view found that the causes were considerations of military security of the USSR, its ideological position and the threat of possible penetration of Islamic fundamentalism in the country. It contributed to making wrong decisions steel as a whole confrontation between the USSR and USA and the balance of power, the deterioration of relations with China, formed in the Kremlin practice of making important state decisions, the personal characteristics of the main persons in the USSR government, the actions of the US administration and their secret services. The novelty of this work is to assess the events as following from the geopolitical situation in the world at that time, but, nevertheless, erroneous, adopted without consideration of other options of solving the problem of security of the USSR. Source base are updated materials of the Politburo of the CPSU Central Committee, related to the subject. In their study of applied systemic-structural method, methods of the analysis of the situation ("research technique") - document analysis and benchmarking, as well as historical-genetic method for studying the events in their development. Author's estimates can be considered during the preparation of textbooks on the history of Russia, history of the Soviet-Afghan relations and international relations.
