Prime purpose of this lecture is to discuss on World War One. Immediate cause of this war is assassination of Archduke Francis Ferdinand by Gavrilo Princip, June 28th, 1914. Some other causes May Include: Industrial Revolution, Militarism, Germany, Nationalism, Serbia, Alliancism, Triple Alliance, Triple Entente, Serbia, Russia, France, Great Britain, US etc. World War One included: three Continents, thirty one Countries, sixty five Million Soldiers, thirty seven Million Casualties, 91,198 Deaths by Gas, 6,395 Allied and Neutral Ships Lost and $186.3 Billion Financial Losses.