World War I Timeline By kwhn97 Jan 1, 1903 Germany challenges Naval supremacy in Europe Jan 1, 1905 Triple Alliance and Triple Entente established May 1, 1905 Gavrilo Princip and Black Hand plan to advance unification of Slavic people Jun 28, 1914 Franz Ferdinand assassinated Jul 28, 1914 Austria-Hungary declares war on Serbia Aug 1, 1914 Germany declares war on Russia Aug 3, 1914 Germany declares war on France Aug 4, 1914 Germany invades Belgium Aug 4, 1914 Great Britain declares war on Germany Aug 27, 1914 Japan joins the Allies in the war Sep 5, 1914 British and French armies stop Germanes at the Marne River Oct 1, 1914 Ottoman Empire joins Central Powers in war Apr 1, 1915 Germans use poison gas against Allied forces Feb 1, 1916 Germans launch Battle of Verdun Jul 1, 1916 French launch Battle of Somme