The tunnels, apparently originally chalk quarries, consisted of three timbered galleries, about 3m wide and 2.3m high, between 120m and 143m in length and joined by a single transverse corridor of 154m. The tunnels ran into the side of the hill with up to 18m of cover, but a series of shafts provided light and ventilation. The maximum capacity was three battalions, one in each gallery, which included battalion headquarters, field kitchens, an aid post and ten days supply of water, food and ammunition. Resupply took place at night by carrying parties. The German front line was on the forward slope of the hill and on the rear slope between the summit and the tunnel entrances there was a line of shelters. The Germans were resolved to hold the hill and placed almost all their manpower within 500m of the front line. Thus two battalions of the 173rd Regiment (223 Division) were deployed in the tunnel or the shelters with the third battalion in reserve.³⁹