Global Conflict (1900-Present)

Established empires weakened as new powers rose after 1900. Japan's victory over Russia in 1905 showed that a non-European state could defeat a great power, and the Ottoman Empire lost territory while Young Turk officers pressed for reform. The Qing dynasty fell in the revolution of 1911, and Sun Yat-sen's republic struggled against regional warlords. In Mexico, revolution against Porfirio Diaz began in 1910 and produced the 1917 constitution, with land reform demands voiced by Emiliano Zapata.

The First World War grew from militarism, alliances, imperial rivalry, and nationalism. Germany's naval buildup alarmed Britain, and rivalry over colonies and the Balkans strained the powers. Two rival blocs, the Triple Alliance and the Triple Entente, turned a local crisis into a continental war. The assassination of Archduke Franz Ferdinand at Sarajevo in June 1914 brought an Austro-Hungarian ultimatum to Serbia, and mobilization pulled Russia, Germany, France, and Britain into the fight within weeks.

The war became a prolonged stalemate fought with industrial weapons. On the Western Front, trenches, machine guns, barbed wire, and artillery made offensives enormously costly, and armies introduced poison gas, tanks, and aircraft. Total war mobilized whole societies through conscription, rationing, censorship, and propaganda, and women entered factory jobs in large numbers. Britain and France drew troops and laborers from India, Africa, and the Caribbean, making the conflict global in manpower as well as reach.

The interwar economy moved from unstable recovery to collapse. The United States stock market crash of 1929 triggered bank failures and a worldwide depression, and new tariffs shrank international trade. Franklin Roosevelt's New Deal from 1933 expanded public works and regulation, while Stalin's five-year plans from 1928 forced Soviet industrialization and collectivized agriculture at enormous human cost. Economic desperation strengthened authoritarian movements in Germany, Italy, and Japan.

The peace settlement left grievances that shaped the following decades. The Treaty of Versailles in 1919 assigned war guilt to Germany, demanded reparations, and stripped away its colonies. The League of Nations was created to keep the peace but had no army and never included the United States. Former Ottoman and German territories became mandates run by Britain and France, frustrating nationalists in the Middle East and Africa. Resentment and economic crisis helped fascists take power under Mussolini and Hitler.

Aggression by expansionist states and the failure of collective security led to a second world war. Japan seized Manchuria in 1931 and invaded China in 1937, and Italy conquered Ethiopia while the League of Nations proved unable to respond. Hitler remilitarized the Rhineland in 1936 and absorbed Austria in 1938, and Britain and France conceded the Sudetenland at Munich rather than fight. The Nazi-Soviet Pact of August 1939 cleared the way for the invasion of Poland that September.

The Second World War was fought across Europe, Asia, Africa, and the Pacific. German blitzkrieg tactics overran Poland and France before the 1941 invasion of the Soviet Union stalled and turned at Stalingrad. Japan's attack on Pearl Harbor in December 1941 brought the United States into the war, and Allied landings in Normandy in 1944 opened a western front. Nazi Germany murdered some six million Jews in the Holocaust, and atomic bombs destroyed Hiroshima and Nagasaki in August 1945.

States and movements killed civilians on a mass scale throughout the century. Ottoman authorities deported and killed Armenians beginning in 1915, and Soviet grain requisitioning produced the Holodomor famine in Ukraine in 1932 and 1933. Japanese forces massacred civilians at Nanjing in 1937, and the Nazi regime industrialized genocide against Jews and Roma. The Khmer Rouge emptied Cambodian cities after 1975, and Hutu extremists killed Tutsi in Rwanda in 1994, prompting international tribunals.

The two world wars shared causes: nationalism, imperial rivalry, alliance commitments, and economic instability, with the unresolved terms of 1919 feeding the crisis of the 1930s. Each conflict widened total war, as states mobilized economies, colonies, and civilians while technology made distant cities targets. Civilians suffered more in each round, from the Armenian genocide to the bombing and death camps of the 1940s. The League of Nations and then the United Nations reflected efforts to break the pattern.