 The battery was defended by a 20 mm anti @-@ aircraft gun and several machine guns in 15 gun positions , all enclosed in an area 700 by 500 yards ( 640 by 460 m ) surrounded by two barbed wire obstacles 15 feet ( 4 @.@ 6 m ) thick by 5 feet ( 1 @.@ 5 m ) high , which also acted as the exterior border for a 100 @-@ yard @-@ deep ( 91 m ) minefield . Another obstacle was an anti @-@ tank ditch covering any approach from the nearby coast . The original commander of the battery , <unk> <unk> , was killed during a Royal Air Force bombing raid on 19 May 1944 . He was replaced by <unk> <unk> Steiner , who commanded 50 engineers and 80 <unk> from the 1st Battery , Artillery Regiment <unk> , part of the 716th Static Infantry Division . 
