Complex sentence: A few hours later, aircraft of the "Regia Aeronautica" (Italian Royal Air Force) raided the harbour castle and the main hills of the small island, where the commandos were entrenched.
Split into simpler sentences: A few hours later, aircraft of the "Regia Aeronautica" (Italian Royal Air Force) appeared over the island. The bombers attacked the harbour castle and the main hills of the small island, where the commandos were entrenched.