Frederick II Hohenstaufen was an enlightened, tolerant, yet absolute king in the Neopolitan realm of the two Sicilies where he studied nature and science from Moors in self-designed castles. Having succeed as German king, he embarked on election as Holy Roman emperor but tired of the quarrelsome electors' endless mistrusting meddling, basically retiring to Italy. Pope Innocent IV condemned the hedonistic falconer fiercely for consorting with infidels, even after he successfully led the Sixth crusade and negotiated without great bloodshed the return of Christian pilgrims to Jerusalem with the sultan's emir (general).