Complex sentence: He survived a civil war in 803 and like most of the Byzantine emperors, he found himself at war on three fronts, suffered a major defeat at the Battle of Krasos in Phrygia in 805 and died on a campaign against the Bulgars.
Split into simpler sentences: He survived a civil war in 803 and, like most of the Byzantine emperors, found himself at war on three fronts. He suffered a major defeat at the Battle of Krasos in Phrygia in 805 and died on a campaign against the Bulgars.