Complex sentence: Although the city had surrendered upon the condition that it would not be plundered, the troops vented their fury on the inhabitants; in the resulting mayhem, known as "Haultpenne's Fury", over 500 citizens were killed.
Split into simpler sentences: Although the city had surrendered upon the condition that it would not be plundered, the troops vented their fury upon the inhabitants. In the resulting mayhem, known as "Haultpenne's Fury", over 500 citizens were killed.