Editing Constantine XI Palaiologos (section)

=== Early career ===
[[File:Map of Constantinople (1422) by Florentine cartographer Cristoforo Buondelmonte.jpg|thumb|1422 map of [[Constantinople]] by cartographer [[Cristoforo Buondelmonti]], the oldest surviving map of the city]]
After an unsuccessful [[Siege of Constantinople (1422)|Ottoman siege of Constantinople in 1422]], Manuel II suffered a [[stroke]] and was left paralyzed in one side of his body. He lived for another three years, but the empire's government was effectively in the hands of Constantine's brother John. Thessaloniki was also [[Siege of Thessalonica (1422–1430)|under siege]] by the Ottomans; to prevent it from falling into their hands, John gave the city to the [[Republic of Venice]]. As Manuel II had once hoped years ago, John hoped to rally support from Western Europe, and he left Constantinople in November 1423 to travel to Venice and Hungary.{{Sfn|Nicol|1992|p=|pp=5–7}} By this time, Manuel had abandoned his hope of western aid and had even attempted to dissuade John from pursuing it. Manuel believed that an eventual church union, which would become John's goal, would only antagonize the Turks and the empire's populace, which could have started a civil war.{{Sfn|Hellebuyck|2006|p=52}}{{better source needed|date=March 2023}}

John was impressed by his brother's actions during the 1422 Ottoman siege,{{Sfn|Hellebuyck|2006|p=6}}{{better source needed|date=March 2023}} and trusted him more than his other brothers. Constantine was given the title of despot and was left to rule Constantinople as regent. With the aid of his bedridden father Manuel, Constantine drew up a new peace treaty with the Ottoman sultan [[Murad II]], who momentarily spared Constantinople from further Turkish attacks. John returned from his journey in November 1424 after failing to procure help. On 21 July 1425, Manuel died and John became the senior emperor, John VIII Palaiologos. Constantine was granted a strip of land to the north of Constantinople that extended from the town of [[Mesembria]] in the north to [[Durusu|Derkos]] in the south. It also included the port of [[Selymbria]] as his appanage in 1425.{{Sfn|Nicol|1992|p=|pp=5–7}} Although this strip of land was small, it was close to Constantinople and strategically important, which demonstrated that Constantine was trusted by both Manuel II and John.{{Sfn|Hellebuyck|2006|p=7}}{{better source needed|date=March 2023}}

After Constantine's successful tenure as regent, John deemed his brother loyal and capable. Because their brother Theodore expressed his discontent over his position as Despot of the Morea to John during the latter's visit in 1423, John soon recalled Constantine from Mesembria and designated him as Theodore's successor. Theodore eventually changed his mind, but John would eventually assign Constantine to the Morea as a despot in 1427 after a campaign there. Though Theodore was content to rule in the Morea, historian Donald Nicol believes that the support was helpful, as the peninsula was repeatedly threatened by external forces throughout the 1420s. In 1423, the Ottomans broke through the ancient [[Hexamilion wall]]—which guarded the Peloponnese—and devastated the Morea. The Morea was also constantly threatened by [[Carlo I Tocco]], the Italian ruler of [[Despotate of Epirus|Epirus]], who campaigned against Theodore shortly before the Ottoman invasion and again in 1426, occupying territory in the northwestern parts of the Morea.{{Sfn|Nicol|1992|p=|pp=7–8}}

In 1427, John VIII personally set out to deal with Tocco, bringing Constantine and Sphrantzes with him. On 26 December 1427, the two brothers reached [[Mystras]], the capital of the Morea, and made their way to the town of [[Glarentza]], which was captured by the Epirotes. In the [[Battle of the Echinades (1427)|Battle of the Echinades]], a naval skirmish off the coast of Glarentza, Tocco was defeated and he agreed to relinquish his conquests in the Morea. In order to seal the peace, Tocco offered his niece, [[Theodora Tocco|Creusa Tocco]]{{sfn|Stathakopoulos|2018|p=245, 247}} (whose name was later changed to the Greek ''Theodora''), in marriage to Constantine, her [[dowry]] being Glarentza and the other Moreot territories. Glarentza was given to the Byzantines on 1 May 1428 and on 1 July, Constantine married Theodora.{{Sfn|Nicol|1992|p=8}}