Complex sentence: Chenevix-Trench, who saved many lives through inspired pseudo-medical advice and hygiene discipline, saw one of his fellow soldiers impaled against a tree with bayonets for attempting to escape, amidst many other horrors.
Split into simpler sentences: Chenevix-Trench saved many lives through inspired pseudo-medical advice and hygiene discipline. He saw one of his fellow soldiers impaled against a tree with bayonets for attempting to escape, amidst many other horrors.