World War I By SthirM Jun 18, 1914 Archduke Ferdinand is killed Jul 28, 1914 Austria-Hungary declares war on Serbia Aug 28, 1914 Germany declares war on Russia France and Belgium Sep 6, 1914 First battle of WWI, the First Battle of Marne is started and trench warfare is first used Nov 5, 1914 Britain and France declare war against the Ottoman empire May 7, 1915 Cruiser Lusitania is sunk May 31, 1916 Britain and German engage in combat off the coast of Jutland Jul 1, 1916 British engage in the First Battle of Somme, the bloodiest day for the British army Mar 15, 1917 Tsar Nicholas II abdicates the throne of Russia Apr 6, 1917 US declares war against Germany Nov 20, 1917 Tanks are first used heavily in combat Nov 11, 1918 Germany and the Allied powers concede to an Armistice