 There were many brick buildings in Siping (city) and bricks made from black earth were extremely tough that when hit by 60 mm mortar rounds, there was only a dent left.The defenders capitalized on these strong buildings and turned them into formidable fortifications, and the nationalist 71st Army headquarters was located in one of such bunkers, with the entrance sealed by a jeep.In addition to wide field of view, there were also dozens bunkers and pillboxes protected by minefields around the buildings to strengthen the defense.