On February 18, 1229, Holy Roman Emperor Frederick II signed a ten year truce with Sultan al Kamil. The truce occurred during the sixth crusade, which had begun in 1228 with the objective of regaining Jerusalem from Egyptian control.
Frederick had sent troops to support the fifth crusade, which ended in failure for the HRE. In 1225, Frederick married Yolonde of Jerusalem, thus gaining a claim to the throne of that city, and direct motivation to crusade. Frederick left for the Holy Land in 1227, but turned back before reaching there. As a result, Pope Gregory IX excommunicated him for breaking his crusader vow. In 1228, Frederick set off again. He found little support in the way of troops along the way, due to his excommunicated status.
Frederick realized that with his small retinue, his best chances lay in negotiation with al-Kamil. Taking this tack, he was able to convince al Kamil, who was preoccupied with a Syrian rebellion of his own, to commit to a truce. This truce enabled Frederick to regain Jerusalem, Bethlehem, Sidon, Jaffa and Nazareth.
One can imagine that Walter Scott would have been interested in Frederick as a supporter of poetry. He was patron for the Sicilian School, which helped develop the Italian language, prior to Dante and Saint Francis of Assisi. Scott covers Frederick in his role as King of Sicily, in "Tales of a Grandfather".
"The Emperor Frederick II. had been heir to the pretensions of the imperial house of Suabia to both the Sicilies ; in other words, to those territories now belonging to the kingdom of Naples. But over these kingdoms the Popes had always asserted a right of homage, similar to that which King John surrendered to the church in England. Upon the death of Frederick, these Italian and Sicilian dominions were usurped by his natural son, called Manfroy, to the prejudice of the emperor's nephew and lawful heir, a youth named Conradin."