World War 1
Battle of Passchendaele
Passchendaele, Belgium
The last large-scale offensive of this period was a British attack (with French support) at Passchendaele (July–November 1917). This offensive opened with great promise for the Allies, before bogging down in the October mud. Casualties, though disputed, were roughly equal, at some 200,000–400,000 per side.