World War I (1914–1918)

Imperial, territorial, and economic rivalries led to the “Great War” between the Central Powers (Austria-Hungary, Germany, Bulgaria, and Turkey) and the Allies (U.S., Britain, France, Russia, Belgium, Serbia, Greece, Romania, Montenegro, Portugal, Italy, and Japan). About 10 million combatants killed, 20 million wounded.

1914: Austrian Archduke Francis Ferdinand and wife assassinated in Sarajevo by Serbian nationalist, Gavrilo Princip (June 28). Austria declares war on Serbia (July 28). Germany declares war on Russia (Aug. 1), on France (Aug. 3), invades Belgium (Aug. 4). Britain declares war on Germany (Aug. 4). Germans defeat Russians in Battle of Tannenberg on Eastern Front (Aug.). First Battle of the Marne (Sept.). German drive stopped 25 miles from Paris. By end of year, war on the Western Front is “positional” in the trenches.

1915: German submarine blockade of Great Britain begins (Feb.). Dardanelles Campaign—British land in Turkey (April), withdraw from Gallipoli (Dec.–Jan. 1916). Germans use gas at second Battle of Ypres (April–May). Lusitania sunk by German submarine—1,198 lost, including 128 Americans (May 7). On Eastern Front, German and Austrian “great offensive” conquers all of Poland and Lithuania; Russians lose 1 million men (by Sept. 6). “Great Fall Offensive” by Allies results in little change from 1914 (Sept.–Oct.). Britain and France declare war on Bulgaria (Oct. 14).

1916: Battle of Verdun—Germans and French each lose about 350,000 men (Feb.). Extended submarine warfare begins (March). British-German sea battle of Jutland (May); British lose more ships, but German fleet never ventures forth again. On Eastern Front, the Brusilov offensive demoralizes Russians, costs them 1 million men (June–Sept.). Battle of the Somme—British lose over 400,000; French, 200,000; Germans, about 450,000; all with no strategic results (July–Nov.). Romania declares war on Austria-Hungary (Aug. 27). Bucharest captured (Dec.).

1917: U.S. declares war on Germany (April 6). Submarine warfare at peak (April). On Italian Front, Battle of Caporetto—Italians retreat, losing 600,000 prisoners and deserters (Oct.–Dec.). On Western Front, Battles of Arras, Champagne, Ypres (third battle), etc. First large British tank attack (Nov.). U.S. declares war on Austria-Hungary (Dec. 7). Armistice between new Russian Bolshevik government and Germans (Dec. 15).

1918: Great offensive by Germans (March–June). Americans' first important battle role at Château-Thierry—as they and French stop German advance (June). Second Battle of the Marne (July–Aug.)—start of Allied offensive at Amiens, St. Mihiel, etc. Battles of the Argonne and Ypres panic German leadership (Sept.–Oct.). British offensive in Palestine (Sept.). Germans ask for armistice (Oct. 4). British armistice with Turkey (Oct.). German Kaiser abdicates (Nov.). Hostilities cease on Western Front (Nov. 11).