Constantinople ultimately fell on 29 May 1453, Constantine XI dying in its defense, ending the Byzantine Empire. In the aftermath of Constantinople's fall, and Constantine XI's death in defense of it, one of the most pressing threats to the new Ottoman regime was the possibility that one of Constantine XI's surviving relatives would find a following and return to reclaim the empire. Luckily for Mehmed II, the two despots in the Morea represented scarcely more than a nuisance and were allowed to keep their titles and lands. When emissaries of Thomas and Demetrios visited the Sultan at Adrianople some months after Constantinople's fall, the Sultan demanded no surrender of territory, only that the despots were to pay an annual tribute of 10,000 ducats. Because the Morea was allowed to continue to exist, many Byzantine refugees fled to the despotate, which made it somewhat of a Byzantine government-in-exile. Some of these influential refugees and courtiers even raised the idea of proclaiming Demetrios, the elder brother, as the Emperor of the Romans and the legitimate successor of Constantine XI. Both Thomas and Demetrios might have considered making their small despotate the rallying point of a campaign to restore the empire, with considerable fertile and wealthy territory under the despotate's control, there did seem for a moment to be a possibility that the empire could live on in the Morea. However, Thomas and Demetrios were never able to cooperate and spent most of their resources fighting each other rather than preparing for a struggle against the Turks. Since Thomas had spent most of his life in the Morea, and Demetrios most of his life elsewhere, the two brothers hardly knew each other.