World War I By hannahdahl Period: Jun 1, 1914 to Jun 30, 1919 WWI Jun 28, 1914 Archduke Franz Ferdinand was Assassinated Jul 23, 1914 Austria's Ultimatum to Serbia Jul 28, 1914 Austria Declares War 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 the 21 Demand to China Feb 19, 1915 Battle of Gallipoli May 7, 1915 Sinking of the Lusitania May 7, 1915 German U-Boat Warfare Begins May 23, 1915 Italy Joins the Allies May 31, 1916 Battle of Jutland Begins Jun 7, 1916 Battle of Verdun Begins Jul 1, 1916 Battle of the Somme Jan 16, 1917 Zimmerman Note Discovered Feb 1, 1917 Unrestricted U-Boat Resumed Apr 6, 1917 America Enters the War Oct 26, 1917 Russian Communist Revolution Begins Mar 3, 1918 Treaty of Brest-Litovsk Signed Sep 26, 1918 Hindenburg Offensive Begins Nov 3, 1918 Meuse-Argonne Offensive Begins Nov 11, 1918 The Armistice is Signed Nov 11, 1918 Kaiser Wilhelm Abdicates Jun 28, 1919 Treaty of Versailles Ends the War