Arc of fire

What kind of bunkers are these and how the Germans used them, described in the memoirs of Daniil Granin. He participated in battles on the so-called 'Appendicitis' - a section of the front at the Pushkin highway in the area of ​​the former village of Kuzmino. There, at a small height was a German stronghold equipped with such bunkers built with railway sleepers. The Soviet troops continuously stormed this stronghold throughout the blockade of Leningrad 1941-1944.