The construction of the infantry bunkers was commissioned on 5 May 1938. During the Nazi occupation the portholes for the main guns were removed from bunker S 31a, while only the anti-tank cannon porthole was removed from bunker S 31b. Both bunkers have been cleaned since 1996 and are undergoing reconstruction.
Infantry bunker StM – S 31a is a one-sided left-wing structure. The bunker was intended to house an anti-tank cannon coupled with a heavy machine gun, a pair of heavy machine guns, a solo heavy machine gun, and three light machine guns.
