From its foundation in 1204 in the wake of the Fourth Crusade, the papacy extended consistent support to the Latin Empire of Constantinople—established by Western crusaders on former Byzantine territory—by conferring crusade indulgences upon those who undertook its defence.
Towards papal legitimisation
Aftermath of the Fourth Crusade
Baldwin I informed Innocent III of his election in a letter that also outlined the circumstances leading to it. He emphasised the alleged disobedience of the Byzantine Church to papal authority. He also accused the Byzantines of duplicity, hostility, and obstructing expeditions to the Holy Land, thereby seeking to justify the crusaders' attack on Constantinople, despite Innocent's earlier rejection of similar arguments. Baldwin further requested that crusading indulgences be granted to those, "both nobles and commoners", who came to defend the Latin Empire, while maintaining that fulfilment of his vow to reach the Holy Land remained his ultimate objective. Without awaiting the Pope's reply, Baldwin appealed directly to other western leaders, including Archbishop Adolph of Cologne, thereby, as Chrissis observes, he effectively "hijacked the crusade".
In his reply to Baldwin's letter of November 1204, Innocent authorised participants of the Fourth Crusade to remain and defend the Latin Empire rather than proceed immediately to the Holy Land. Emphasising that their presence in Constantinople was essential for the defence of the Holy Land, he granted them crusade indulgences. In April or May 1205, he further instructed them to remain there for one year, although without releasing them from their ultimate obligation to campaign in the Holy Land thereafter. Later in May, he extended crusading indulgences to new recruits, arguing that Baldwin's position first had to be secured if the expedition to the Holy Land was to continue. In Chrissis's view, these measures "constitute an important turning point", as Innocent sanctioned "the use of crusading mechanisms" for the defence of the Latin Empire, justifying this policy by reference to the protection of the Holy Land and the union of the churches.
Crusade of Bishop Nivelon of Soissons
Kaloyan of Bulgaria entered into negotiations with Pope InnocentIII on the eve of the Fourth Crusade. In exchange for recognising papal supremacy over the Bulgarian Orthodox Church, Innocent offered him a royal crown. Seeking to strengthen his international position, Kaloyan accepted, but requested the title of tsar for himself and that of patriarch for the head of the Bulgarian Church. Innocent dispatched a papal legate to Bulgaria, who crowned Kaloyan king on 7November 1204 and granted the Bulgarian prelate the title of primate, thus only partially fulfilling Kaloyan's request. Kaloyan did not renounce his claims and continued to style himself tsar.
In the aftermath of the sack of Constantinople, Kaloyan began to assert control over Thrace, seizing territories from local Greek (aristocrats). Although he was prepared to reach a compromise with the Latins regarding the division of the region, they sought to assume possession of all former Byzantine lands. They also refused to confirm the Thracian in their holdings, intending instead to distribute the hinterland of Constantinople among themselves. In response, the Greeks rose in open rebellion and sought Kaloyan's protection. After the Greeks of Adrianople expelled the Latin garrison and submitted to him, Baldwin I advanced against the city without waiting for reinforcements. His forces were defeated at the city on 14April 1205 by Kaloyan and his Cuman allies. Captured on the battlefield, Baldwin was taken prisoner, and Kaloyan informed the pope of his death in July 1206. Baldwin was succeeded by his brother Henry, who was crowned emperor on 20August.
Meanwhile, the two papal legates in the East, Cardinals Peter Capuano and Soffred, left the Crusader states for Constantinople, where they released the crusaders from their obligation to proceed to the Holy Land. In July 1205 Pope Innocent sharply rebuked this decision, having recently learned of the atrocities committed during the sack of Constantinople. That same month Henry, acting as regent for his captive brother, wrote to the Pope urging him to proclaim a crusade across Catholic Europe. He pointed to Kaloyan's expansionism and the Greek rising in Thrace, attributing recent disasters to the sins of the Latins. The letter was carried by Nivelon de Quierzy, Bishop of Soissons, together with the knights Nicholas of Mailly and John Bliaud. In response, Innocent issued an encyclical granting crusade indulgences to those who took up arms in defence of the Latin Empire, maintaining that Latin control of Constantinople offered "hope, for sure, that Jerusalem will be liberated from the pagans". Acting as regent for the underage Frederick of Sicily, he also granted the crusaders safe passage to Apulia and arranged their transport from Brindisi, instructing them to notify him of their expected arrival.
Bishop Nivelon circulated letters combining extracts from Henry's appeal and the papal encyclical granting indulgences. At the same time, Innocent informed Kaloyan of the projected crusade, urging him to release Baldwin and reach an accommodation with the Latins. From Rome, Nivelon travelled to north-eastern France and Flanders to preach the crusade, carrying relics with him. Henry's brother, Philip I of Namur, appears to have been designated its leader, as Innocent urged him in April 1206 to set out for Constantinople. In the same letter the Pope released participants from all other pilgrimage vows, except those relating to the Holy Land. According to Chrissis, this marks the first documented instance of vow commutation. Philip, however, withdrew from the enterprise and declined to contribute financially. Despite this setback, the contemporaneous records that "an innumerable multitude of clergy, monks, and laymen, were inflamed with the zeal of faith" and took the cross.
The conclusion of the crusade remains uncertain. Bishop Nivelon died at Bari in September 1207. The medievalist Walter Norden and the Byzantinist Ernst Gerland state that the crusading forces "dispersed" following his death; however, as Chrissis observes, they provide no conclusive evidence in support of this claim. By contrast, an early redaction of the chronicle of Niketas Choniates, composed in the early 1210s, records the crusaders' arrival at Dyrrachion and their defeat by Michael I Komnenos Doukas, the Greek ruler of Epirus, during their eastward advance. Nicholas of Mailly and John Bliaud returned to the Latin Empire, where they campaigned against the Bulgarians in 1207–08. Around the turn of 1207 and 1208, a further contingent of crusaders, dispatched by Philip of Namur, reached Constantinople under the command of Peter of Douai. They subsequently served in the army of Henry, engaging both Boril of Bulgaria, successor to Kaloyan, and the rebellious Lombard lords in the Kingdom of Thessalonica.
Crusading rhetoric
Following the Battle of Adrianople, Kaloyan captured Serres and Philippopolis. The imprisonment and execution of numerous inhabitants drove the Greek population to seek rapprochement with the Latins, enabling Emperor Henry and King Boniface of Thessalonica to preserve Latin authority in Thrace and Macedonia. After Boniface was killed in a skirmish with Bulgarian raiders on 4September 1207, he was succeeded by his underage son, Demetrius, under the regency of his mother, Margaret of Hungary. The local Lombard aristocracy, however, opposed her rule and elected one of their own, Hubert of Biandrate, as guardian to the child king. Kaloyan was unable to capitalise on the situation, as he died under uncertain circumstances before the walls of Thessaloniki in October. His eleven-year-old son, Ivan Asen, was compelled to seek exile, and the throne passed to Kaloyan's nephew, Boril, who proved unable to assert effective authority over the recalcitrant frontier magnates.
Emperor Henry summoned Hubert to Constantinople in order to exact his oath of fealty, but the latter refused, prompting Henry to march on Thessaloniki. Despite the resistance of the Lombard lords, Henry secured Thessaloniki with the support of Margaret and her adherents and crowned Demetrius king in January 1209. Hubert and his supporters fled to Boeotia, but Henry pursued them and compelled their submission by early summer. The Latin defeat at Adrianople enabled Theodore Laskaris to consolidate and extend his authority in western Anatolia. In 1208 he convened a synod at his capital, which elected Michael Autoreianos as ecumenical patriarch. On Easter Sunday, Michael crowned Theodore emperor, thereby affirming his claim to be the lawful successor of the Byzantine emperors. The growing prominence of crusading concepts in the Greek world was reflected, circa 1208–10, in Patriarch Michael's grant of indulgences to those who took up arms against the Latins.
To secure support in the West, the Latins of Constantinople frequently employed crusading imagery and rhetoric, presenting themselves as champions of the Church and their opponents as its foes. From the outset, the Latin emperors regularly dispatched relics to western rulers to foster enthusiasm for crusading efforts in defence of their empire. Henry, in particular, was active in cultivating western backing. His campaigns were at times framed by crusading rituals: soldiers made confession and received communion, while attending prelates promised plenary indulgences. During his campaign against Boril, for example, the chaplain Philip accompanied the army bearing a relic of the True Cross. Philip carried the same relic to the Battle of Philippopolis, where he granted absolution to the warriors, who subsequently advanced with the crusading cry, "Holy Sepulchre!". Henry's triumphalist proclamations concerning his victories over his Greek and Bulgarian adversaries habitually invoked divine favour and concluded with appeals for reinforcements from the West, pointedly reminding his correspondents of the small number of troops at his disposal. The Latins maintained that the foundation of their empire was an expression of divine providence and that its defence therefore constituted a service to God. This interpretation was swiftly taken up by western intellectuals, leading the Cistercian abbot Arnaud Amaury to describe a tripartite crusading movement in which the "schismatics of the East" were numbered among the enemies. From the early 1210s, Pope Innocent's efforts to recruit troops for the Latin Empire declined as his focus shifted to a crusade for the recovery of the Holy Land. He nevertheless supported Henry by forbidding Catholics, on pain of excommunication, to enter the service of the rulers of Epirus and Nicaea. In April 1213 he proclaimed the Fifth Crusade, yet the bull was not circulated in the Latin Empire, suggesting he did not expect its forces to take part.