"In six weeks during April and May 1915, as World War I escalated, Germany forever altered the way war would be fought with poison gas, torpedoes killing civilians, and aerial bombardment. Each of these actions violated rules of war carefully agreed at the Hague Conventions of 1898 and 1907. The era of weapons of mass destruction had dawned. While each of these momentous events has been chronicled in histories of the war, historian Diana Preston...