In 2022, Russia launched a war against Ukraine. Politicians and diplomats in various countries are trying to find ways to end it. So far, however, all attempts have been in vain. This is primarily because people in the West are accustomed to seeking the causes of wars in politics and economics, whereas the current war between Russia and Ukraine was triggered by ideology. This book analyzes the main tenets of Russian state ideology: the symbiosis of church and state, the concept of the Third Rome, and the theory of the Russian World. The first two ideologemes originated in Byzantium but were adopted by the Russians and taken to extremes. The third ideologeme originated in Russia itself and has developed particularly strongly in recent decades. The book also examines the role Ukraine plays in Russian state ideology and explains why Russia does not need Ukraine´s territory or resources, but rather Ukraine as a whole-without which Russian state ideology loses its core. Particular attention is devoted to Crimea, which Russia occupied in 2014 and whose status sparks lively debate in the West