7 – Bulgarian & Nicaean Forces (1235)
After Constantinople was sacked during the Fourth Crusade in 1204, a new Empire, known as the Latin Empire, was formed by the leaders of the conquest. They set up their empire on lands acquired from the Byzantines and on May 16, 1204, Baldwin I was crowned as the first Emperor. The Latin Empire lasted less than 60 years as it failed to establish any sort of dominance. Also, the Latin’s only had a relatively small amount of territory; other states claimed to be the successor to the Eastern Roman Empire including the Empire of Nicaea.
However, the Latin Empire did include Constantinople, the capital of the Byzantine Empire, which was coveted by various entities. By the late 1220s, the Nicaea Empire emerged as the biggest threat to the Latin Empire as it began acquiring territories in Greece. The Nicaean Emperor, John III Doukas, forged an alliance with Bulgaria (and its leader Ivan Asen II) and in 1235, the combined might of the new allies attempted to take Constantinople.
The Latin Empire’s leader, Emperor John of Brienne, was trapped in the city but the second Duke of the Archipelago, Angelo Sanudo, intervened on behalf of Constantinople by sending a naval squadron to help John of Brienne. As a result, the Latin’s were able to hold off the invaders until the winter forced the Bulgar/Nicaean alliance to retreat. Despite initially agreeing to continue the siege in 1236, Asen refused to send troops. John of Brienne died in 1237, and the Bulgars broke the treaty with Nicaea because of the possibility of Asen becoming the Latin Empire’s regent.
However, the Nicaeans refused to quit and continued their plan to regain Constantinople. They had the city more or less surrounded by 1247, and a victory at the Battle of Pelagonia in 1259 was the beginning of the end of the Latin Empire. Although Michael VIII Palaiologos failed to take Constantinople in a siege in 1260, the Nicaeans finally landed their prize on July 25, 1261. Instead of embarking on yet another lengthy siege, a general named Alexios Strategopoulos found an unguarded entrance and claimed the city for Emperor Michael VIII.