Murad II then formed a new army called Azeb in 1421 and marched through the Byzantine Empire and laid siege to Constantinople. While Murad was besieging the city, the Byzantines, in league with some independent Turkish Anatolian states, sent the sultan's younger brother Küçük Mustafa (who was only 13 years old) to rebel against the sultan and besiege Bursa. Murad had to abandon the siege of Constantinople in order to deal with his rebellious brother. He caught Prince Mustafa and executed him. The Anatolian states that had been constantly plotting against him — Aydinids, Germiyanids, Menteshe and Teke — were annexed and henceforth became part of the Ottoman Sultanate.
Murad II then formed a new army called Azeb in 1421 and marched through the Byzantine Empire and laid siege to Constantinople While Murad was besieging the city, the Byzantines, in league with some independent Turkish Anatolian states, sent the sultan's younger brother Küçük Mustafa (who was only 13 years old) to rebel against the sultan and besiege Bursa. Murad had to abandon the siege of Constantinople in order to deal with his rebellious brother. He caught Prince Mustafa and executed him. The Ana.tolian states that had been constantly plotting against him — Aydinids, Germiyanids, Menteshe and Teke — were annexed and henceforth became part of the Ottoman Sultanate.