apart, the first trench () to be occupied by sentry groups, the second () to accommodate the front-trench garrison and the third trench in which local reserves would assemble. The trenches were to be traversed and have sentry-posts in concrete recesses in the parapet. Dugouts were to be deepened from to , set apart and be large enough for each. An intermediate line of strong points (the ) designed for all-round defence, about behind the front line was also to be built. Communication trenches were to be dug back to the enlarged reserve line, renamed the second position, which was as well built and wired as the first position. The second position was built beyond the range of opposing field artillery, to force an attacker to stop and move guns and ammunition forward before assaulting the line. Behind the German front line, the ground rose steeply to the west for , to the top of Thiepval ridge, higher than the Ancre valley. Construction of a small network of trenches, known as (Swabian Fieldworks), began on the ridge in early 1915, roughly north of Thiepval, at the northern and highest point on the ridge. About further back, a second position (the Grandcourt Line to the British), was dug south from Grandcourt to Pozières, with a line of new (redoubts), , , , and . was developed into Redoubt) and connected to Mouquet Farm by , Thiepval wood by and to Thiepval village by . The redoubt dominated Thiepval, the ground to the south and St Pierre Divion to the north-west. With Stuff and Pommiers redoubts, the Germans had observation in all directions and garrisons which could reinforce the front line or deliver a counter-attack. Redoubt had deep dugouts for accommodation with several entrances each, a battalion command post, first aid post, signalling station and strong points, with three heavy machine-guns and four light machine-guns. Many of the dug-outs were on the perimeter, at trench junctions (clockwise from north, using the English names), Irwin Trench (strong points 49 and 69), Lucky Way (strong point 27), Stuff Trench, Hessian Trench (strong point 45), Martin's Lane, the Strasburg Line (strong point 19) and Clay Trench (strong point 99). Inside the redoubt, along an inner trench on the south-west face, were strong points 65, 37 and 39. Beyond the south-west face, in the maze of trenches towards Thiepval to the south and St Pierre Divion