History influenced 1917

The date in the title is doing work. The film is set on 6 April 1917, during the German withdrawal to the Hindenburg Line, and most of what the two men walk through is that withdrawal rather than a battle. From the record: the ground given up deliberately and left ruined behind them, the felled orchards, the poisoned wells and the booby-trapped dugouts; the trench system and the gap between the lines; the Devonshire Regiment; and the plain fact that an order to call off an attack travelled at the speed of a man walking, or did not arrive. The landscape they cross is reconstructed from photographs.