World War I spanned four years and involved all the major nation states of the world. Here's a brief timeline of the sequence of events during the war:
1914 — The War Begins
June 28: Archduke Franz Ferdinand, heir to the throne of Austro-Hungarian empire, in Sarajevo, Bosnia, assassinated.
August: Outbreak of war. Britain and Japan enters fray, Germany declares war on France, Russia, invades Belgium, U.S. declares policy of neutrality
August 14: Battle of the Frontiers begins, settles down into stubborn trench warfare
October: Turkey enters war
December 25: Unofficial Christmas truce declared by soldiers
1915 — Allied Disappointments, German Successes
February: Russians suffer heavy losses in Winter Battle. Allied troops besieged by Turkish forces in Gallipoli, Turkey.
April: First use of poison gas by Germany. France, Russia, Italy, Britain conclude secret Treaty Of London
May: U-boat sinks British liner Lusitania with the loss of American lives, creating a U.S.-German diplomatic crisis. Italy declares war on Austria-Hungary.
August: Germans capture Warsaw
December: Allies begin withdrawal of troops from Gallipoli
1916 — The Fiercest Fighting
February: Germans attack Verdun, defended by France at great cost to both sides: over 700,000 dead, wounded or missing. It was the war's longest battle, lasting till December.
May: Battle of Jutland, the biggest naval battle in history, ultimately without a clear victor. Proved to be tactical victory for Germany, but strategic victory for the British.
June: Russian Brusilov offensive in Carpathia nearly knocks Austria-Hungary out of the war.
July: Battle of the Somme begins, provides greatest number of casualties in British military history: 60,000.
1917 — The U.S. Enters The Fray
January: Germany announces unrestricted submarine warfare, threatening commercial U.S. ships.
February: U.S. severs diplomatic ties with Germany.
March: British capture Baghdad.
April 6: U.S. declares war on Germany.
June: First U.S. troops arrive in France. Greece enters the war on the side of the Allies.
July: T.E. Lawrence and the Arabs capture Aquaba.
December: Jerusalem falls to Britain. Russia opens separate peace negotiations with Germany.
1918 — Allied Advances To Armistice
March: Soviet Russia concludes separate peace negotiations in treaty of Brest-Litovsk. Germany launches five major offensives against Allied forces.
May: U.S. forces victorious in first major action, Battle of Cantigny.
July: Allies counterattack against German forces, seizing initiative. Former Tsar Nicholas II, his wife, and children, are murdered by the Bolsheviks.
October: Germany and Austria send peace notes to U.S. President Woodrow Wilson requesting an armistice, Germany ceases unrestricted submarine warfare, Turkey concludes armistice.
November: Trieste falls to the Allies; Austria-Hungary concludes an armistice, as does Germany, Kaiser Wilhelm II abdicates and flees to Holland, German republic is founded.
November 11: Armistice day, fighting ceases at 11 a.m.
1919 — Peace
Paris Peace Conference leads to the signing of the Treaty of Versailles. The perceived injustice of the terms of the peace treaty imposed upon Germany by the victorious Allies led, historians argue, to the rise of Hitler and WWII.
By Raksha Shetty