sentences:  A couple of the large underground structures continued to be used long after as military hardware storage, and some still are to this day, by the once again independent Czech Army.The basic philosophy of the design was a mutual defensive line, that is, most of the firepower was directed laterally from the approaching enemy.The facing wall of all the fortifications, large and small, was the thickest, covered with boulders and debris, and covered again with soil so even the largest caliber shells would have lost most of their energy before reaching the concrete.