The Somme sector of the Western Front was held by French forces until early 1916, when the British and Dominions Third and Fourth Armies moved into the northern part, before the joint First Battle of the Somme from July to November 1916. In 1917, with the German withdrawal to the Hindenburg Line, British responsibility moved further south. By early 1918 the British Third and Fifth Armies were responsible as far south as east of Noyon. In Spring 1918...