Henry III promised his party-follower Berthold the Duchy of Swabia. However, Henry's widow Agnes of Poitou gave the Duchy in fief to Rudolf of Rheinfelden in 1057. Berthold received, as compensation for the abandonment of his claim to the Duchy, the titles to Carinthia and Verona, whereby the Zähringen ascended to the status of a mediatized house. In Carinthia and Verona, though, Berthold was never really accepted as ruler.
Through his enmity with Henry IV, and his favor with Friedrich I, Duke of Swabia, Berthold's claims were in danger. In the end, the Zähringen were able to maintain their position.