Complex sentence: Indeed, while Conrad II and Louis VII refused to pay homage to the Byzantine emperor in the fall of 1147, and thus retain the Byzantine troops, Roger II seized Corfu and Cephalonia, and plundered Corinth and Thebes.
Split into simpler sentences: Indeed, while Conrad II and Louis VII refused to pay homage to the Byzantine emperor in the fall of 1147, and yet retain Byzantine troops. Consequently, Roger II seized Corfu and Cephalonia, and plundered Corinth and Thebes.