In September 1946 the territory was made part of the new state of Rhineland-Palatinate, along with former left bank territories of Prussia (southern part of the Rhine Province, including the former Principality of Birkenfeld which had been an exclave of Oldenburg until 1937, and western parts of the Province of Nassau) and Rhenish Hesse. The former Territory of the Saar Basin was reinstated and expanded to create the French Saar Protectorate, which returned to Germany in 1956 as the modern state of Saarland.