Complex sentence: James I, in order to minimize losses, save lives and keep the city intact, was in favour of reaching an agreement, but the relatives of the Montcadas and the bishop of Barcelona demanded revenge and extermination.
Split into simpler sentences: James I, in order to cut losses, save lives and get an intact city, was in favour of reaching an agreement. The relatives of the Montcadas and the bishop of Barcelona demanded revenge and extermination.