The communes were strong enough to confine German Emperor Frederick Barbarossa's Italian ambitions to the south, where he secured Sicily for his Hohenstaufen heirs by marrying his son into the Norman royal family.
Barbarossa's son fell in love with a woman from Italy.
mnli hypothesis: Barbarossa's son fell in love with a woman from Italy. premise: The communes were strong enough to confine German Emperor Frederick Barbarossa's Italian ambitions to the south, where he secured Sicily for his Hohenstaufen heirs by marrying his son into the Norman royal family.