The szlachta ([ˈʂlaxta] ( listen), exonym: Nobility) was a legally privileged noble class with origins in the Kingdom of Poland. It gained considerable institutional privileges between 1333 and 1370 during the reign of King Casimir III the Great.:211 In 1413, following a series of tentative personal unions between the Grand Duchy of Lithuania and the Crown Kingdom of Poland, the existing Lithuanian nobility formally joined this class.:211 As the Polish-Lithuanian Commonwealth (1569–1795) evolved and expanded in territory, its membership grew to include the leaders of Ducal Prussia, Podolian and Ruthenian lands.

What class was slackta in Poland?