Complex sentence: Because he had fallen behind their trench-lines, they took the responsibility of interring him in Keerselaarhock Cemetery, being re buried at Hinter den Linden after the war.
Split into simpler sentences: Because he had fallen behind their trench-lines, they took the responsibility of interring him in Keerselaarhock Cemetery. He was reinterred at Hinter den Linden after the war.