The Outbreak of War By brie2127 Jun 28, 1914 The Archduke Franz Ferdinand was assassinated in Sarajevo. Jul 28, 1914 Austria declared war on Serbia Jul 29, 1914 Russia mobilised Aug 1, 1914 Germany declared war on Russia Aug 1, 1914 France mobilised in support of Russia Aug 2, 1914 Germany demands free passage through Belgium to fight France Aug 3, 1914 Germany declared war on France and thus invaded Belgium Aug 4, 1914 Britain as ally to Belgium, declared war on Germany