John of Brienne ( 1170 – 19–23 March 1237) was the king of Jerusalem from 1210 to 1225 and Latin emperor of Constantinople from 1229 to 1237. He was the youngest son of Erard II of Brienne, a wealthy nobleman in Champagne. John, originally destined for an ecclesiastical career, became a knight and owned small estates in Champagne around 1200. After the death of his brother Walter III, he ruled the County of Brienne on behalf of his minor nephew Walter IV, who lived in Italy.

The barons of the Kingdom of Jerusalem proposed that John marry Maria, the heir to the kingdom. With the consent of Philip II of France and Pope Innocent III, he left France for the Holy Land; in 1210, he married Maria and they were crowned king and queen. After Maria's death in 1212, John administered the kingdom as regent for their infant daughter, Isabella II. Maria's influential uncle, John of Ibelin, attempted to depose him. King John was a leader of the Fifth Crusade. Although his claim of supreme command of the crusader army was never unanimously acknowledged, his right to rule Damietta (in Egypt) was confirmed shortly after the city fell to the crusaders in 1219. He claimed the Armenian Kingdom of Cilicia on behalf of his second wife, Stephanie, in 1220. After Stephanie and their infant son died that year, John returned to Egypt. The Fifth Crusade ended in failure (including the recovery of Damietta by the Egyptians) in 1221.

John was the first king of Jerusalem to visit Europe (Italy, France, England, León, Castile and Germany) to seek assistance for the Holy Land. He gave his daughter in marriage to Holy Roman Emperor Frederick II in 1225, and Frederick ended John's rule of the Kingdom of Jerusalem. Although the popes tried to persuade Frederick to restore the kingdom to John, the Jerusalemite barons regarded Frederick as their lawful ruler. John administered papal domains in Tuscany, became the podestà of Perugia and was a commander of Pope Gregory IX's army during Gregory's war against Frederick in 1228 and 1229.

John was elected emperor of the Latin Empire in 1229 as the senior co-ruler of Baldwin II, and he was crowned in Constantinople in 1231. John III of Nicaea and Ivan Asen II of Bulgaria occupied the last Latin territories in Thrace and Asia Minor, besieging Constantinople in early 1235. John directed the defence of his capital during the months-long siege, with the besiegers withdrawing only after Geoffrey II of Achaea and united fleets from Italian towns defeated their fleet in 1236. The following year, John died as a Franciscan friar.

Early life John was the youngest of the four sons of Count Erard II of Brienne and Agnes of Montfaucon. He seemed "exceedingly about 80"George Akropolites: The History (ch. 27.), p. 184. to the 14-year-old George Akropolites in 1231; if Akropolites' estimate was correct, John was born around 1150. However, no other 13th-century authors described him as an old man. John's father referred to John's brothers as "children" in 1177 and mentioned the tutor of the oldest brother, Walter, in 1184; this suggests that John's brothers were born in the late 1160s. Modern historians agree that John was born after 1168, probably during the 1170s.

John's father destined him for a clerical career, but according to the late-13th-century Tales of the Minstrel of Reims, John "was unwilling". Instead, the minstrel continued, John fled to his maternal uncle at the Clairvaux Abbey. Encouraged by his fellows, he became a knight and earned a reputation in tournaments and fights. Although elements of the Tales of the Minstrel of Reims are apparently invented (for instance, John did not have a maternal uncle in Clairvaux), historian Guy Perry wrote that it may have preserved details of John's life. A church career was not unusual for youngest sons of 12th-century noblemen in France; however, if his father sent him to a monastery he left before reaching the age of taking monastic vows. John "clearly developed the physique that was necessary to fight well" in his youth, because the 13th-century sources Akropolites and Salimbene di Adam emphasize his physical strength.

John's father, Erard II, joined the Third Crusade and died in the Holy Land in 1191. His oldest son, Walter III, succeeded him in Brienne. John was first mentioned in an 1192 (or 1194) charter issued by Walter, indicating that he was a prominent figure in his brother's court. According to a version of Ernoul's chronicle, John participated in a war against Peter II of Courtenay. Although the Tales of the Minstrel of Reims claimed that he was called "John Lackland", according to contemporary charters John held Jessains, Onjon, Trannes and two other villages in the County of Champagne around 1200. In 1201, Theobald III of Champagne granted him additional estates in Mâcon, Longsols and elsewhere. Theobald's widow, Blanche of Navarre, persuaded John to sell his estate at Mâcon, saying that it was her dower.

Walter III of Brienne died in June 1205 while fighting in southern Italy. His widow, Elvira of Sicily, gave birth to a posthumous son, Walter IV, who grew up in Italy. John assumed the title of count of Brienne, and began administering the county on his nephew's behalf in 1205 or 1206. As a leading vassal of the count of Champagne, John frequented the court of Blanche of Navarre, who ruled Champagne during the minority of her son, Theobald IV. According to a version of Ernoul's chronicle, she loved John "more than any man in the world"; this annoyed King Philip II of France.

The two versions of Ernoul's chronicle tell different stories about John's ascent to the throne of Jerusalem. According to one version, the leading lords of Jerusalem sent envoys to France in 1208 asking Philip II to select a French nobleman as a husband for their kingdom's heir, Maria. Taking advantage of the opportunity to rid himself of John, Philip II suggested him. In the other version an unnamed knight encouraged the Jerusalemite lords to select John, who accepted their offer with Philip's consent. John visited Pope Innocent III in Rome. The pope donated 40,000 marks for the defence of the Holy Land, stipulating that John could spend the money only with the consent of the Latin patriarch of Jerusalem and the grand masters of the Knights Templar and the Knights Hospitaller.

King of Jerusalem

Co-ruler

John landed at Acre on 13 September 1210; the following day, Patriarch of Jerusalem Albert of Vercelli married him to Maria. John and Maria were crowned king and queen in the Cathedral of Tyre on 3 October. The truce concluded by Maria's predecessor Aimery and the Ayyubid sultan Al-Adil I had ended by John's arrival. Although Al-Adil was willing to renew it, Jerusalemite lords did not want to sign a new treaty without John's consent. During John and Maria's coronation, Al-Adil's son Al-Mu'azzam Isa pillaged the area around Acre but did not attack the city. After returning to Acre, John raided nearby Muslim settlements in retaliation.

Although about 300 French knights accompanied John to the Holy Land, no influential noblemen joined him; they preferred participating in the French Albigensian Crusade or did not see him as sufficiently eminent. John's cousin, Walter of Montbéliard, joined him only after he was expelled from Cyprus. Walter led a naval expedition to Egypt to plunder the Nile Delta. After most of the French crusaders left the Holy Land, John forged a new truce with Al-Adil by the middle of 1211 and sent envoys to Innocent III urging him to preach a new crusade.

Conflicts Queen Maria died shortly after giving birth to her and John's daughter, Isabella, in late 1212. Her death triggered a legal dispute, with John of Ibelin questioning the widowed king's right to rule. John of Ibelin was Maria's uncle and had served as her regent prior to her marriage to John. The king sent Ralph of Mérencourt, the bishop of Sidon, to Rome for assistance from the Holy See. Innocent III confirmed John as lawful ruler of the Holy Land in early 1213, urging the prelates to support him with ecclesiastical sanctions if needed. Most of the Jerusalemite lords remained loyal to the king, acknowledging his right to administer the kingdom on behalf of his infant daughter; John of Ibelin left the Holy Land and settled in Cyprus.

The relationship between John of Brienne and Hugh I of Cyprus was tense. Hugh ordered the imprisonment of John's supporters in Cyprus, releasing them only at Innocent's command. During the War of the Antiochene Succession John sided with Bohemond IV of Antioch and the Templars against Raymond-Roupen of Antioch and Leo I of Armenia, who were supported by Hugh and the Hospitallers. However, John sent only 50 knights to fight the Armenians in Antiochia in 1213. Leo I concluded a peace treaty with the Knights Templar late that year, and he and John reconciled. John married Leo's oldest daughter, Stephanie (also known as Rita), in 1214 and Stephanie received a dowry of 30,000 bezants. Quarrels among John, Leo I, Hugh I and Bohemond IV are documented by Innocent III's letters urging them to reconcile their differences before the Fifth Crusade reached the Holy Land.

Fifth Crusade

Innocent proclaimed the Fifth Crusade in 1213, with the "liberation of the Holy Land" (the reconquest of Jerusalem) its principal object. The first crusader troops, commanded by Leopold VI of Austria, landed at Acre in early September 1217. Andrew II of Hungary and his army followed that month, and Hugh I of Cyprus and Bohemond IV of Antioch soon joined the crusaders. However, hundreds of crusaders soon returned to Europe because of a famine following the previous year's poor harvest. A war council was held in the tent of Andrew II, who considered himself the supreme commander of the crusader army. Other leaders, particularly John, did not acknowledge Andrew's leadership. The crusaders raided nearby territory ruled by Al-Adil I for food and fodder, forcing the sultan to retreat in November 1217. In December John besieged the Ayyubid fortress on Mount Tabor, joined only by Bohemond IV of Antioch. He was unable to capture it, which "encouraged the infidel", according to the contemporary Jacques de Vitry.

Andrew II decided to return home, leaving the crusaders' camp with Hugh I and Bohemond IV in early 1218. Although military action was suspended after their departure, the crusaders restored fortifications at Caesarea and Atlit. After new troops arrived from the Holy Roman Empire in April, they decided to invade Egypt. They elected John supreme commander, giving him the right to rule the land they would conquer. His leadership was primarily nominal, since he could rarely impose his authority on an army of troops from many countries.

The crusaders laid siege to Damietta, on the Nile, in May 1218. Although they seized a strategically important tower on a nearby island on 24 August, Al-Kamil (who had succeeded Al-Adil I in Egypt) controlled traffic on the Nile. In September, reinforcements commanded by Pope Honorius III's legate Cardinal Pelagius (who considered himself the crusade's supreme commander) arrived from Italy.