Support WBURWWI: The Battle That Split Europe, And FamiliesPlay07:49Download AudioNPR StaffApril 30, 2011 ShareSoldiers care for the wounded on the first day of the Battle of Passchendaele on July 31, 1917. Fought in West Flanders, Belgium, Passchendaele was one of the war's most costly clashes. (Imperial War Museum, London)