After the king had won some recognition in Southern Germany, he started a campaign to Italy, where he hoped to crush the rule of Gian Galeazzo Visconti over the thriving Duchy of Milan and to be crowned Holy Roman Emperor by the Pope.

The Luxembourg resistance waned after Wenceslaus was arrested at Prague Castle by his brother Sigismund in March 1402 and the next year his lordship was finally recognized by the Pope.

Rupert also gained the support of England by the marriage of his son Louis with Blanche of Lancaster, daughter of King Henry IV on 6 July 1402.

After attempts to enlarge the king's allodium caused conflicts with his former ally, the Archbishop of Mainz forging an alliance with Count Eberhard III of Württemberg, the Zähringen margrave Bernard I of Baden and several Swabian cities in 1405, Rupert was compelled to make certain concessions.

The quarrel was complicated by the Papal Schism, but the king was just beginning to make some headway when he died at his castle of Landskrone near Oppenheim on 18 May 1410 and was buried at the Church of the Holy Spirit in Heidelberg.