A Higher Form of Killing: Six Weeks in World War I That Forever Changed the Nature of Warfare

In six weeks during April and May 1915, as World War I escalated, Germany forever altered the way war would be fought. On April 22, at Ypres, German canisters spewed poison gas at French and Canadian soldiers in their trenches; on May 7, the German submarine U-20, without warning, torpedoed the passenger liner Lusitania, killing 1,198 civilians; and on May 31, a German Zeppelin began the first aerial bombardment of London and its inhabitants. Each of these actions violated rules of war care...