The major event that marked the beginning of the end for European monarchies was World War I, which lasted from 1914 to 1918. The war led to significant societal and political changes across Europe. The immense human and economic costs resulted in widespread disillusionment with monarchies, particularly in countries like Russia, Germany, Austria-Hungary, and the Ottoman Empire. As a result, several empires collapsed, giving rise to republics and new political structures. The Russian Revolution of 1917 epitomized this shift, as the tsar was overthrown, marking the decline of monarchies and the emergence of new ideologies, paving the way for modern democratic and socialist movements.