The magnates of Poland and Lithuania (magnateria) were an aristocracy of Polish-Lithuanian nobility (szlachta) that existed in the Crown of the Kingdom of Poland, in the Grand Duchy of Lithuania and, from the 1569 Union of Lublin, in the Polish–Lithuanian Commonwealth, until the Third Partition of Poland in 1795. The magnate social class arose around the 16th century and, over time, gained more and more control over Commonwealth politics. The most powerful magnates were known as "little kings" due to the extent of their power and independence. Their influence diminished with the Third Partition of Poland (1795), which ended the Commonwealth's independent existence, and came to an end with the Second World War and the communist-ruled People's Republic of Poland. Famous magnate families in the territories of the Crown of Poland included the Czartoryski, Kalinowski, Koniecpolski, Ostrogski, Potocki, Tarnowski, Wiśniowiecki, Zasławski and Zamoyski families; and in the Grand Duchy of Lithuania, the Kieżgajłow, Olelkowicz, Radziwiłł, Pac and Sapieha families. The magnates arose as the wealthiest and most politically powerful social class, part of the nobility (szlachta), of the Kingdom of Poland and Grand Duchy of Lithuania, around 16th century. Their powers waned after the Commonwealth loss of independence following its final partition in 1795, but they would remain a significant power in the culture, politics and economy of the Polish territories until World War II. Magnates (or higher nobility) vied for political power with the lesser and middle nobility (Ruch egzekucyjny in the late 16th century, and the reform movement of the Great Sejm in the late 18th century) and the King. To be counted among the magnates, one should have a large estate, and political influence at least on the scale of a province, if not national. Regional differences abounded, with the estates being much larger in the east, where the wealthier magnates were also much more likely to have their own private armies.