Attack on Constantinople

At the Battle of Ankara (1402), Timur's Mongols routed Bayezid I's forces. In the aftermath, a civil war of succession broke between Bayesid’s sons. 
The Byzantines exploited the situation and signed a peace treaty with their Christian neighbors and with one of Bayezid's sons. Thus, they were able to recover Thessalonica and much of the Peloponnese. The Ottoman civil war ended in 1413 when the favorite of Byzantium, Mehmet I, defeated his opponents. 
The rare amity between the two states did not last; the death of Mehmet I and the rise of Murad II in 1421 coupled with the assumption of John VIII Palaiologos to the Byzantine throne led to a deteriorated change in relations between the two. John VIII made the first and foolish move by inciting a rebellion in the Ottoman Empire: a certain Mustafa had been released by the Byzantines and claimed that he was Bayezid's lost son 
Despite the odds, a sizable Byzantine force (mostly mercenaries) was assembled in Europe under his banner, defeating a Turkish army. Murad's furious reply eventually smashed this initial success and, in 1422, began the Siege of Thessalonica and of Constantinople.

The first full-scale Ottoman Siege of Constantinople took place in 1422 
When Murad II emerged as the winning successor to his father, he marched into Byzantine territory. The Turks had acquired their own cannon for the first time by the siege of 1422: "falcons", which were short but wide cannon.[ The two sides were evenly matched technologically, and the Turks had to build barricades in order to receive the stones of the bombards. 
The Byzantine defenders won the battle and the Turks had to lift the siege suffering severe casualties. The Greeks, though, still had to pay an increased tribute to the Turks.

Byzantines	Ottoman Turks
Commander	Commander
Emperor John VIII	Sultan Murad II
Forces	Forces
Unknown	Unknown
Casualties	Casualties
—	Heavy

Noteworthy or unique facts about this battle:

Contemporary Byzantine tradition ascribed the deliverance of Constantinople to a miraculous intervention by the Virgin Mary (Theotokos).

The Battles of History