The paper, which consists of two articles, explores development of the Syrian crisis in 2011–2020. In this article, internal and external factors of the crisis are explained. The internal socio-economic and political situation before the crisis is analyzed. The author shows, on the basis of the IMF Data and the scientific research, that the internal situation in Syria was better by a lot of indicators in comparison with the other countries, in which the protest movements of the Arab Spring took place and cannot have been the cause of the acute crisis. The main factor of the confrontation was the support of external actors for the armed Syrian opposition, which is composed in majority of the radical Islamist groups. The presence in their rangs of thousands of the fighters-djihadists, including foreign citizens stimulated appearing in Syria the hearth of the radical Islamism and the arising of so-called Islamic State (ISIS) . The author analyses the goals of the leading countries of NATO, including Turkey, and the monarchies of the Persian Gulf. They used the armed opposition, including its radical forces to try to change the regime in Syria and to realize their interests in the region. The author concludes that the main cause of so lasting continuation of the Syrian crisis is the actions of the external actors, who are illegitimately present in Syria. In the following article, which is planned for publishing, special attention is directed to examine the new stage of the Syrian crisis, which came after the ISIS crush.