Latin Empire of Constantinople in the context of "Ivan Asen II of Bulgaria"

The Crusades were a series of military campaigns launched by the papacy between 1095 and 1291 against Muslim rulers for the recovery and defence of the Holy Land (Palestine), encouraged by promises of spiritual reward. The First Crusade was proclaimed by Pope Urban II at the Council of Clermont on 27 November 1095 in response to a Byzantine appeal for aid against the advancing Seljuk Turks. By this time, the papacy's position as head of the Catholic Church had strengthened, and earlier conflicts with secular rulers and wars on Western Christendom's frontiers had prepared it for the direction of armed force in religious causes. The First Crusade led to the creation of four Crusader states in the Middle East, whose defence required further expeditions from Catholic Europe. The organisation of such large-scale campaigns demanded complex religious, social, and economic institutions, including crusade indulgences, military orders, and the taxation of clerical income. Over time, the crusading movement expanded to include campaigns against pagans, Christian dissidents, and other enemies of the papacy, promoted with similar spiritual rewards and continuing into the 18th century.

The Crusade of 1101, the earliest papally sanctioned expedition inspired by the First Crusade, ended in disastrous defeats. For several decades thereafter, only smaller expeditions reached the Holy Land, yet their role in consolidating and expanding the Crusader states was pivotal. The fall of Edessa, the capital of the first Crusader state, prompted the Second Crusade, which failed in 1148. Its failure reduced support for crusading across Latin Christendom, leaving the Crusader states unable to resist Saladin's expansion. Having united Egypt and Muslim Syria under his rule, Saladin destroyed their combined armies at the Battle of Hattin in 1187. The Crusader states survived largely owing to the Third Crusade, a major campaign against Saladin, though Jerusalem remained under Muslim control. Initially directed against Egypt, the Fourth Crusade was diverted to the Byzantine Empire, culminating in the Sack of Constantinople and the establishment of the Latin Empire in 1204. The Fifth Crusade again targeted Egypt but failed to conquer it in 1219–21. By this period, crusade indulgences could also be obtained through other campaigns—such as the Iberian, Albigensian, and Northern Crusades—thereby diminishing enthusiasm for expeditions in the eastern Mediterranean.

Peter II of Courtenay (French: Pierre de Courtenay; died c. late 1217) was emperor of the Latin Empire of Constantinople in 1217.

The King of Thessalonica was the ruler of the Kingdom of Thessalonica, one of the crusader states founded in Greece in the aftermath of the Fourth Crusade (1202–1204). The King of Thessalonica was not an independent ruler; the Kingdom of Thessalonica was one of several vassal states created by the crusaders, subservient to the new Latin Empire of Constantinople, which had supplanted the Byzantine Empire.

The kingdom proved to be short-lived, with Thessalonica being captured by Theodore Komnenos Doukas of Epirus in 1224, just twenty years after the kingdom had been founded. The last king, Demetrius of Montferrat, escaped into exile and upon his death ceded the title to Frederick II, Holy Roman Emperor, who some years later ceded it back to Demetrius's family. Their line of titular Kings of Thessalonica ended with the marriage of Yolande of Montferrat to Byzantine emperor Andronikos II Palaiologos in 1284, at which point titular ownership of Thessalonica passed back to the Byzantine emperors.

Theodore II Doukas Laskaris or Ducas Lascaris (Greek: Θεόδωρος Δούκας Λάσκαρις, romanized: Theodōros Doúkās Láskaris; November 1221/1222 – 16 August 1258) was Emperor of Nicaea from 1254 to 1258. He was the only child of Emperor John III Doukas Vatatzes and Empress Irene Laskarina. His mother was the eldest daughter of Theodore I Laskaris, who had established the Empire of Nicaea as a successor state to the Byzantine Empire in Asia Minor after the crusaders captured the Byzantine capital, Constantinople, during the Fourth Crusade in 1204. Theodore received an excellent education from two renowned scholars, Nikephoros Blemmydes and George Akropolites. He made friends with young intellectuals, especially with a page of low birth, George Mouzalon. Theodore began to write treatises on theological, historical and philosophical themes in his youth.

Emperor John III arranged for Theodore to marry Elena Asenina in 1235, to forge an alliance with her father, Ivan Asen II, Emperor of Bulgaria, against the Latin Empire of Constantinople. According to Theodore himself, their marriage was happy, and they had five or six children. From 1241, Theodore acted as his father's lieutenant in Asia Minor during his frequent military campaigns in the Balkan Peninsula. From around 1242, he was his father's co-ruler, but was not crowned as co-emperor. During this period, his relationship with some prominent aristocrats, particularly Theodore Philes and Michael Palaiologos, grew tense.

Geoffrey I of Villehardouin (French: Geoffroi I de Villehardouin) (c. 1169 – c. 1229) was a French knight from the County of Champagne who joined the Fourth Crusade. He participated in the conquest of the Peloponnese and became the second prince of Achaea (1209/1210–c. 1229).

Under his reign, the Principality of Achaea became the direct vassal of the Latin Empire of Constantinople. He extended the borders of his principality.