A portion of the former eastern territo east of the Lubusz Land had previously formed the western parts of the Polish provinces of Pomerelia and Greater Poland (Polonia Maior), being lost to Prussia in the First Partition (the Pomerelian parts) and the Second Partition (the remainder). During Napoleonic times the Greater Poland territories formed part of the Duchy of Warsaw, but after the Congress of Vienna Prussia reclaimed them as part of the Grand Duchy of Posen (Poznań), later Province of Posen. After World War I, those parts of the former Province of Posen and of West Prussia that were not restored as part of the Second Polish Republic were administered as Grenzmark Posen-Westpreußen (the German Province of Posen–West Prussia) until 1939.