Germany Declares War on Russia, Escalating World War I
Following the assassination of Archduke Franz Ferdinand in June 1914, Austria-Hungary declared war on Serbia on July 28. Russia, Serbia's ally, mobilized its forces. Germany, bound by alliance to Austria-Hungary, issued an ultimatum to Russia to halt mobilization. When Russia refused, Germany declared war on Russia on August 1, 1914. France, allied with Russia, ordered general mobilization the same day. German troops soon crossed into Luxembourg, setting the Schlieffen Plan in motion for a two-front war. Within days, Britain entered the conflict after Germany invaded Belgium, transforming a regional crisis into a global war.
