The German Army realised that shortening the front line by retiring to better prepared positions would reduce the demand for manpower and offer better defensive capabilities. Accordingly the German engineers constructed what the British referered to as The Hindenburg Line in the sector of the Western Front largely behind (to the East of) the 1916 Somme battlefield. The retreat was done in stages. The official dates covering this period are 14 March to 5 April 1917.
