Frederick Barbarossa vs. Pope Alexander III over Lombardy, Italy and its resources.
Frederick wanted to be able to contest German factions. To do this he needed wealth and resources. The easiest way in the eyes of Frederick to obtain such was to sack Lombardy and loot it. The Pope contested him, siding with the Italian province. Frederick, upset at this new obstacle, burned Milan to the ground. Frederick supported “anti-pope” Pascal III, rejected Alexander III, wanting to rid the barrier between him and more power. Frederick died later while on a Crusade.
The Hohenstaufen family vs. Welf family.
The papacy sided with Welf candidate Otto, believing that, with so many Hohenstaufens in office, a new family should act as a balance. Otto was crowned Holy Roman Emperor. He invaded southern Italy against the Pope, seeking to unite Sicily and Italy, and wanted to annex the lands of the Old Roman Empire. Frederick II, a Hohenstaufen, replaced Otto as emperor because the high officers in the church grew fearful of Frederick. The pope and other high church leaders became wary of his ambition and excommunicated Frederick, soon afterward. 1241, a new Pope, Innocent III, deposes Frederick from office of emperor.