An example of the political purpose crusades: German emperor Friedrich II's expedition to the east

Six years after the Fifth Crusade (1217-1221) organized to Egypt failed, Holy Roman Emperor and King of Sicily Frederick II von Hohenstaufen was sailed from Brindisi in September 1227 to realize the Crusade, which was delayed for ye-ars, to strengthen his prestige in Europe by taking Jerusalem back from the Muslims and to establish domination in the Latin East as the ruler of the Christians. However, when some of his soldiers died due to the epidemic at that time and he was infected with it, he had to return to Italy. Although he made Crusader vows many times be-fore the excuse of sickness of Frederick II whose vow was not completed by himself was re¬jected by Pope Gregorious IX and the judgement of his excommunicate was given off. Meanwhile, after the death of his wife, who was named Queen of Jerusa-lem, he lost the title of "King of Jerusalem". However, Frederick eventually sailed to the East on 28 June 1228, as the excommunicated Crusader and as custodian of his younger son, King Konrad. Before he sailed, he had contacted the Egyptian Ayyûbid Sultan, al-Kāmil, who was in search of an ally against his brother and his rival, the ruler of Da¬mascus, al-Mu'azzam, and gained his friendship to some extent. The first stop of Fre¬derick's Crusade was the Cyprus Crusader Kingdom, on which he claimed high autho¬rity. After struggling with the Ibelin dynasty for a while in Cyprus, he took the bailliage (regent) of Henry, the king of the kingdom, who had not yet reached his adulthood, from the hands of the Ibelines. Frederick, who then came to Acre on 7 September 1228, met with a great opposition here as well. Since the army next to him was not enough for a military victory, he obtained what he wanted through dip-lomacy. Thus, Sultan contacted al-Kāmil through the ambassadors and discussed the delivery of Jerusalem to him. As a result of these negotiations in which both rulers exhibited their political bargaining abilities, an agreement was reached. By the Tre-aty of Jaffa, signed on 18 February 1229, Jerusalem and its surroundings, whose walls were destroyed, were handed over to the Crusaders on condition that Muslims worship freely. Frederick en¬tered the Jerusalem after the treaty and wore the crown of his own on 18 March 1229; nobody attended the ceremony because it was excommunicated. Upon receiving the news that the church armies attacked the his kingdom in Southern Italy, the emperor embarked the ship in Acre to return to his country on 1 May 1229. Frederick, who later made peace with the pope and removed the excommunicate, tried to remotely rule the Crusader Kingdom through a regent sent to the East, but this caused a civil war in the kingdom.