IOTL, Constantine Angelos was a successful military leader who led the Byzantines to a strong of important victories against the Vlachs and Bulgars. He was going to attempt to overthrow his ineffective cousin, Isaac II, but was betrayed by several of his officers on his way to Adrianople.
What if his officers had remained loyal to him and he had successfully overthrown his cousin in 1193?
What if his officers had remained loyal to him and he had successfully overthrown his cousin in 1193?