WWI Timeline By agusmerotti Jun 28, 1914 Archduke Franz Ferdinand is assassinated Jul 23, 1914 Austria's Ultimatum to Serbia Jul 28, 1914 Austria declares was on Serbia Aug 4, 1914 Britain declares war on Germany Aug 26, 1914 Battle of Tannenberg begins Sep 6, 1914 First Battle of the Marne begins Oct 19, 1914 Trench Warfare begins Jan 18, 1915 Japan presents Twenty-One Demands to China Feb 19, 1915 Battle of Gallopoli Apr 26, 1915 Italy joins the Allies May 7, 1915 German U-boat warfare begins May 7, 1915 Sinking of the Lusitania May 31, 1916 Battle of Jutland begins Jun 7, 1916 Battle of Verdun begins Jul 1, 1916 Battle of the Somme Jan 9, 1917 Unrestricted U-boat resumed Jan 16, 1917 Zimmerman Note Discovered Apr 7, 1917 America enters the war Oct 26, 1917 Russian Communist Revolution begins Nov 11, 1917 Kaiser Wilhelm abdictates Mar 3, 1918 Treaty of Brest-Litovsk is signed Sep 26, 1918 Hindenburg Offensive begins Nov 3, 1918 Meuse-Argonne Offensive begins Nov 11, 1918 The Armistice is signed Jun 28, 1919 Treaty of Versailles ends the war