World War I

The First World War, a global conflict from 1914 to 1918, was fought between the Allied and Central Powers. It remains one of history’s deadliest wars, with an estimated 15 to 22 million deaths, including those from war crimes and genocides, and it also contributed to the spread of the Spanish flu pandemic. The war saw the first large-scale use of machine guns, artillery, aircraft, chemical weapons, and tanks. Its causes included the rise of the German Empire, which disrupted Europe’s balance of power, and intensified imperial rivalries that fueled new alliances and an arms race. Tensions in the Balkans reached a breaking point on 28 June 1914, when Gavrilo Princip assassinated Archduke Franz Ferdinand. Austria-Hungary declared war on Serbia on 28 July, prompting Russia to mobilize in Serbia’s defense. Germany then declared war on Russia and France, and invaded Belgium, bringing the United Kingdom into the war. Germany’s initial strategy to quickly defeat France stalled in September, leading to a static Western Front of fortified trenches from the English Channel to Switzerland. The Eastern Front was more fluid but indecisive. The Ottoman Empire joined the Central Powers in November, followed by a failed Allied campaign at Gallipoli. Japan and Italy joined the Allies. Major battles at Verdun, the Somme, and Passchendaele failed to break the stalemate. In April 1917, the United States entered the war after Germany resumed unrestricted submarine warfare. Later that year, the Bolsheviks seized power in Russia, leading to an armistice with the Central Powers in December and a separate peace in March 1918. Germany launched a spring offensive in March 1918, but it left its army exhausted. The Allied Hundred Days Offensive from August 1918 collapsed the German front. By early November, armistices were signed with the Ottomans and Austria-Hungary, leaving Germany isolated. Kaiser Wilhelm II abdicated on 9 November, and the war ended on 11 November 1918. The Paris Peace Conference imposed the Treaty of Versailles, which disarmed Germany, stripped it of territories, and required heavy reparations. The collapse of the Russian, German, Austro-Hungarian, and Ottoman empires created new states like Poland, Finland, the Baltic states, Czechoslovakia, and Yugoslavia. The League of Nations was established but failed to prevent World War II.