The crusade of Frederick II ended differently than any before or after: By treaty and without a single sword blow, the Emperor gained control over the highly symbolic cities of Jerusalem, Nazareth and Bethlehem in March 1229.
Frederick had achieved his goal through skillful and pragmatic action. Among other things, he exploited his knowledge of Arabic sciences to hold stimulating discussions about mathematics and other scientific topics with the sultan during the long and arduous negotiations about Jerusalem.
How important this was for the success of the mission, anyone who has even once has haggled over prices at the bazaar can tell you. Ideas that seem so far apart that a compromise may appear at first completely unthinkable may be resolved at an astonishing speed provided you refrain from duping the opposite party and keep on talking terms.
These two rules were taken to heart by Frederick and the sultan. They sent senior envoys and made valuable gifts to affirm each other of the importance of the issue and how much they appreciate each other. And before they sat down to haggling over cities, they turned the conversation to more harmless subjects in order to build trust and thus to prepare the ground for an agreement on the Holy City. Frederick knew these forms of oriental negotiation and applied them successfully. But does this make him a friend to Muslims?
Stefan Leder, orientalist at the University of Halle, was able to demonstrate a few years ago that a body of Arab historical texts exist to which can be traced the history of the special kindness of the Muslim emperor. That they will be cited over and over again in today's multicultural world doesn’t make it true in any way.
There are three men’s writings that fed the myth. First and foremost is Sibt Ibn al-Gauzi (died 1257). He was one of the most important chroniclers of his time - and not especially well-disposed towards Frederick. He remarked that the value of the emperor at the slave market would probably be less than ten Darahim (which happens to be the plural of Dirham). That would not be much for even an average slave. Al-Gauzi held a sermon in Damascus against the return of Jerusalem to the Christians. The policy of the Emperor, however, didn’t seem to be transparent to him and he suggested that Christianity could possibly be a smoke screen for Frederick.
The second chronicler who contributed to the myth of Frederick Muslim connection was Ibn Wasil Gamal al-Din (1207 to 1298). As a boy he had witnessed Al-Gauzi’s preaching in Damascus. Later, he spent time as ambassador at the court of King Manfred, Frederick's son and successor in the kingdom of Sicily. He wrote that the emperor once asked Sultan Al-Kamil for permission to visit Jerusalem, and that the sultan had permitted it. In addition, he delivered this famous story: "The Qadi Shams ad-Din, Kadi of Nablus, said: I ordered the muezzins not to call to prayer that night out of respect for him (the emperor). When we woke up and I came to him, he said to me, O kadi, why have the muezzins not called to prayer, as is their habit? I said to him: This slave has forbidden this in deference to the king, and out of respect for him. To this replied Frederick, You erred in what you have done. By God, it was my greatest desire to listen to the night prayer of the muezzins and their worship of God when spending the night in Jerusalem."
Reference: Book ‘Kreuzzug und Herrschaft unter Friedrich II. Handlungsspielräume von Kreuzzugspolitik (1215–1230), Mittelalterforschung Bd. 13’; Author ‘Bodo Hechelhammer’; Publisher ‘Thorbecke’; Published ‘Ostfildern, 2003’. Book ‘Kaiser Friedrich II. (1194–1250). Herrscher, Mensch, Mythos.’; Author ‘Hubert Houben’; Publisher ‘Kohlhammer’; Published ‘Stuttgart e.a. 2008’. Article ‘Der Staufer Friedrich II. und die Geschichtsschreibung des 19. und 20. Jahrhunderts.’; Author ‘Hannes Obermair’; Publisher ‘Concilium Medii Aevi’; Published ‘Stuttgart, 2008’. Book ‘Stupor mundi. Zur Geschichte Friedrichs II. von Hohenstaufen. Wege der Forschung Bd. 101’; Editor ‘Gunther Wolf’; Publisher: ‘Wege der Forschung Wissenschaftliche Buchgesellschaft’; Published ‘Darmstadt, 1982’.