Germans making an organized retreat to the Hindenberg Line.
*In March 1917, the German armies on the Somme carried out a strategic withdrawal known as Operation Alberich. They destroyed everything on the ground that they left: flattening villages, poisoning wells, cutting down trees, blowing craters on roads and crossroads, booby-trapping ruins and dugouts. The withdrawal was to a more powerful shorter line, positioned to take tactical advantage of ground. British patrols began to detect the withdrawal of German infantry from the Somme in mid February 1917 and a cautious pursuit began, halted only as the Hindenburg Line itself was approached.