Complex sentence: Bayezid surrendered and was executed, according to Doukas on the insistence of Junayd; his brother, Hamza Bey, was spared the same fate because Junayd Mustafa entered Edirne in triumph.
Split into simpler sentences: Bayezid surrendered and was executed--according to Doukas, on the insistence of Junayd. His brother, Hamza Bey, was spared because Junayd Mustafa entered Edirne in triumph.