1917 - February Revolution: the overthrow of the Russian monarchy and establishment of a provisional government.1941-1945 - World War II: the Soviet Union fights against Nazi Germany on the Eastern Front, leading to significant casualties and destruction.1991 - Dissolution of the Soviet Union: the collapse of the communist regime and the establishment of the Russian Federation as an independent state.1999 - Second Chechen War: the conflict between Russian forces and Chechen separatists results in significant civilian casualties and destruction in the region.2014 - Annexation of Crimea: Russia's controversial annexation of Crimea from Ukraine, leading to international condemnation and sanctions against Russia.