In June 1203 the crusaders of the 4th crusade attacked the city of Constantinople on request of the Byzantine prince Alexius. Alexus III fled the city and the prince took the throne as Alexus IV along with his blind father Isaac II. After taking the throne it was time to pay up the crusading army what he promised them, but soon Alexus IV ran short of money. Soon he faced an anti-Latin hatred, becoming unpopular and finally he was toppled in a palace coup in January 1204. The crusaders cheated of their reward, declared war on Byzantine and took the city in April 1204. Before the capture of the city, the Crusaders decided that 12 electors, 6 Venetians and 6 Franks, should choose an emperor who would rule ¼ of Byzantine’s territory and the other ¾ would be divided. Baldwin of Flanders became the first emperor of the Latin Empire, and the Venetian Thomas Morosini was chosen as a patriarch.
Organization of the empire
The empire was organized on the western feudal principles, with small elements of the Byzantine administration. The elite of the empire were the Frankish and Venetian lords, headed by the emperor, the barons and the lower-ranking vassals and liege lords, including many former Byzantine aristocrats. The emperor was assisted by a council of barons, Venetian podesta (chief magistrate of the city, high official in Italian cities), and another council with only 6 members. Since Venice had high influence in the Latin Empire, and held part of Constantinople, the podesta was very important and influential, practically independent from the emperor. The council vas very influential too, especially in times of regency. Right after the conquest of the city, the Latins completely rejected the Byzantine economic administration. This disrupted all the production and trade, forcing the Latin Empire to request help from the papacy in the begging. They exported wheat and fur from Thrace and profited from the strategic location of Constantinople for trade, but this was not enough. In 1230 Constantinople had a shortage of food even with reduced population. The only economic profit that was actually blooming was the sale of relics to Western Europe from the looted Byzantine churches. Emperor Baldwin II is known to have sold the Crown of Thorns in France.
The organization of the church was changed too. All the Orthodox hierarchy was replaced with Roman Catholic prelates, under supervision of the Latin archbishop and the Papal legate. Later, in 1231 the two offices merged. Western Catholic monastic orders, such as the Cistercians, the Dominicans and the Franciscans were established in the empire. The Orthodox clergy retained its rights and customs, including its right to marriage, but was demoted to a subordinate position, subject to the local Latin bishops.
Warafare
The crusaders initiated a military campaign in the Asian Minor and by 1205 they captured most of Bithynia. In 1207 a truce was signed with Theodore I Laskaris, emperor of Nicaea. They won another victory at the Rhyndakos River in 1211, and in 1214 another treaty was signed. Meanwhile, the situation in Europe was different. The Byzantine lords in Thrace called the Bulgarian tsar Kaloyan for help. The Latin knights suffered a heavy defeat from the Bulgarians and the Cumans at the Battle of Adrianople in 1205. The emperor Baldwin was captured and imprisoned in a tower in Tarnovo and latter that year died as prisoner. The tower still bears the name Baldwin’s Tower. The throne was taken by Henry of Flanders, who reclaimed most of the lost territories in Thrace from the Bulgarians after the death of Kaloyan in 1207. In 1210 peace was signed and Henry married Maria of Bulgaria, daughter of Kaloyan. Another threat to the Latin was Michael I Komnenos Doukas, Despot of Epirus. In 1209, the daughter of Michael I married Henry’s brother. This allowed Henry to invade Macedonia, Thessaly and Central Greece, but Michael attacked the Kingdom of Thessalonica in 1210, forcing Henry to comeback and help the city. While supervising the repairs to the walls of Thessalonica, Henry died and was succeeded by Peter of Courtenay in 1216. His reign didn’t last long since he was captured and executed by Theodore Komnenos Doukas, who succeeded Michael I in 1214. The throne was taken by Yolanda of Flanders, Peter’s wife until 1219 when she died too. The regency continued until 1221 when Robert of Courtenay came back to Constantinople. The war with Nicaea was continued in 1222. In the battle of Poimanenon in 1224, the Latin army was defeated. Epirus used the moment when the Latins were destructed with Nicaea, and in 1224 took Thessalonica. Epirus conquered Thrace in 1225-1226 and reached the gates of Constantinople, but Theodore was threatened by the Bulgarian king Ivan II Asen, so truce was concluded in 1228. Meanwhile all territories in Asia were lost except for Nicomedia.
The fall of the Latin Empire
In 1228 Robert died and John of Brienne became new the regent of the empire. The threat of Epirus was removed by the Bulgarians. However, Nicaea under the rule of John III Doukas Vatatzes, conquered some territories in Greece and made alliance with Bulgaria. In 1235 they sieged Constantinople but were unsuccessful. In 1237 Baldwin II came to the Latin throne. The empire was very weak, so he often traveled to West Europe looking for help, but without any success. He was desperate for money, so much that he removed the roof of the Great Palace and sold it. He even gave his only son Philip to Venetian merchants as a guarantee for a loan. By 1247 Nicaea surrounded Constantinople. The battle of Pelagonia in 1558 was the beginning of the end of the Latin Empire. In 1261, the Nicaean general Alexios Strategopoulos entered Constantinople, restoring Byzantine for Michael VIII Palaiologos.
After Constantinople was taken, ending the Latin Empire, Baldwin II still continued to use the tittle Emperor of Constantinople. Even his heirs continued to use this tittle, although they would never rule the city again.