In 1813 the Kingdom of Prussia occupied large amounts of Saxony's territory in the Battle of Leipzig, including the Electoral Circle (which had been renamed the "Wittenberg Circle" in 1807); in May 1815 a treaty was signed in which Saxony ceded this territory to Prussia. In June 1815 they all became part of the German Confederation. In 1816 Prussia reorganised its annexed territory, merging it with the former Duchy of Magdeburg, Principality of Halberstadt, Principality of Erfurt, the Eichsfeld, and the former Imperial Cities of Mühlhausen and Nordhausen, along with the Altmark and other parts of Brandenburg west of the Elbe, into the Province of Saxony.