The front held by the 36th Division was in its natural features not ill adapted for defence. It was crossed by a series of ridges and valleys running east and west, parallel to the front line. Behind the front-line system, which was on the same ridge as the German outposts and on its reverse slope, was a deep valley known as Grugies Valley, from Grugies to the St. Quentin-La Fère Road, north of Urvillers, thence curving northward into "No Man's Land," towards Neuville-St. Amand. Grugies Valley had therefore its advantages and its dangers. On the one hand it afforded good masked positions for machine-guns; on the other, it was a conduit, from the north-eastern end of which attack might flow down behind the line of resistance of the Forward Zone. Behind it was another ridge, upon which was the Line of Redoubts. Behind this again the ground sloped away gradually, rising to a slighter ridge, along which ran the Essigny-Contescourt Road. Upon the forward and reverse slopes of this last ridge were the positions of the two southern sectors of the Battle Zone, four thousand five hundred yards behind the front line. The northern sector, as has been explained, was north of the St. Quentin Canal. These positions were good, but they had one great failing. The front line of the 36th Division ran roughly from west to east to Sphinx Wood, while thence the line of the 14th Division ran more nearly north and south. The right flank was therefore very insecure. Should Urvillers fall, the right of the 36th Division's Forward System would undoubtedly crumple, while should such a calamity as the capture of Essigny occur, the defences of the Battle Zone would be turned.