Complex sentence: Several times, especially in 759, Paul feared that the Greek emperor would send an armament against Rome; and he lived in continual dread lest Byzantine machinations turn the Frankish influence in favor of the Lombards.
Split into simpler sentences: Several times, especially in 759, Paul feared that the Eastern Roman Emperor would send an armament against the city of Rome. Paul lived in continual dread lest Eastern Roman ambitions turn the Frankish influence in favor of the Lombards.