In spite of the arrangement with the Union, Tilly then devastated the Rhenish Palatinate, and in February 1623 Maximilian was formally invested with the electoral dignity and the attendant office of imperial steward, which had been enjoyed since 1356 by the Counts Palatine of the Rhine.
In March 1647 Maximilian concluded the Truce of Ulm (1647) with France and Sweden, but the entreaties of Ferdinand III, Holy Roman Emperor led him to disregard his undertaking.