The Empire also gained Mount Athos and coastal land of the Black Sea from Constantinople to Varna. As an added bonus, Imperial authority was asserted over a number of Aegean Islands. The importance of the latter should not be underestimated as these would serve in the future as refuge for any seeking to escape Ottoman expansion, even if only as a temporary refuge. Bayezid's sons lost no time fighting each other for their father's shattered realm. By 1413, Mehmed I had emerged as the victor. However, the Byzantines had made sure to support the victor and Mehmed I did not forget the kindness of the Byzantines and was able to "control" his Turk subjects from expanding into Byzantine territory. Resumption of hostilities Manuel II Palaiologos was 70 years of age in 1421 and believed that the time had come for him to retire and give his eldest son, John VIII, the opportunity to rule with a more aggressive manner than he had done so. At the same time, a far less restrained Murad II, son of Mehmed I, came to the Ottoman throne in May of that year. With two men uninterested in diplomacy on the thrones of Byzantium and the Ottoman Sultanate, war was inevitable. The Byzantines were the first to make a move when John VIII and his advisors made a risky decision by inciting a rebellion within the Ottoman Sultanate. In August 1421, they backed a man named Mustafa who claimed to be a long lost son of Bayezid the Thunderbolt. In Europe, Mustafa's rebellion worked well and he gathered some support. However, in August 1422, Murad II had this rebellion crushed and Mustafa received the traditional execution (hanging) shortly after, something any rebel would have expected. Murad II was enraged and had an army sent to Constantinople and to Thessalonika, the latter falling in 1430. Murad II was unable to take Constantinople by force. Nonetheless, the situation in the Capital was dire enough for Manuel II to come out of retirement and incite yet another rebellion in Asia Minor under Murad II's brother, Kucuk Mustafa. Initial rebel success, including a siege of Bursa was too much for Murad II to ignore so the siege of Constantinople was lifted to deal with this threat, and to the Byzantines' greatest despair, dealt with it successfully. Manuel II was now out of tricks to save the erroneous rule of