 Complete the following phrase:  Depth of defence works was up to 5 kilometers; they were connected by the radio, but walls of some bunkers were so thick that operators had to go outside. In every bunker there were up to 30 soldiers of the Border Defence Corps KOP; they were equipped with 75 mm cannons and machine guns. The Border Defence Corps Regiment Sarny, which operated the Area, was very well trained, and its soldiers, including Władysław Raginis, distinguished themselves during the 