Complex sentence: The inhabitants of some castles without defenses are immediately killed, while the inhabitants of the defended castles consider the revolt only a nuisance since they consider their high-tech castles unchallengeable.
Split into simpler sentences: The inhabitants of some castles without defenses are immediately killed, while the inhabitants of the defended castles consider the revolt only a nuisance. Complacently they consider their high-tech castles unchallengeable.