Complex sentence: During the Second World War he had been leading dozens of people to safety, walking them beyond the Gothic Line, crossing, roped together in the darkness, the well known Apennine Mountains, where he had born and lived with his wife and their nine children.
Split into simpler sentences: During the Second World War he led dozens of people to safety, crossing with them over the Gothic Line. While roped together in the darkness, they crossed the well-known Apennine Mountains, where he had been born and later lived with his wife and their nine children.