Four type M272 regelbau ("standard design") casemates requiring 600 cubic metres of concrete and four tons of reinforcing steel were built, with walls and roofs over 2 m (6.6 ft) thick.Each casemate held a 15 cm TbtsK C/36 naval gun, manufactured by the German-controlled Škoda Works in Plzeň, Czechoslovakia, with a range of approximately 20 km (12 mi) and a rate of fire of six to eight rounds per minute.Fire control was managed from a regelbau type M262A two-story command post located on the cliff edge 300 m (980 ft) forward of the guns.The battery returned fire at 06:05, and at 06:20 targeted the headquarters ship for Gold Beach, HMS Bulolo, which withdrew out of range.The French cruisers Georges Leygues and Montcalm, assisted by the World War I vintage dreadnought USS Arkansas, returned fire, knocking out one casemate and damaging two others.