the use of Lithuanian Calvinists. Royal court The second important channel for the spread of the Polish language and culture was the royal and grand ducal court. After 1447, only for short periods there was a separate grand ducal court in Vilnius. But even then the Polish influence was strong. Already Grand Duke Vytautas employed Polish secretaries to run his Latin chancellery. The Krakow court was dominated by Poles who travelled with the king to Lithuania. The Lithuanian nobles who joined the court were therefore greatly influenced by Polish culture. Casimir Jagiellon was the last grand duke to know Lithuanian. From the time of Zygmunt August, correspondence with the Lithuanian elite was conducted almost exclusively in Polish, since the knowledge of Latin in Lithuania was too weak. Ruthenian lands Jogaila's successor Władysław III of Varna, who reigned in 1434–1444, expanded the privileges of the nobles to all Ruthenian nobles irrespective of their religion, and in 1443 signed a bull equalizing the Orthodox church in rights with the Roman Catholicism thus alleviating the relationship with the Orthodox clergy. These policies continued under the next king Casimir IV Jagiellon. Still, the most cultural expansion of the Polish influence continued since the Ruthenian nobility were attracted by both the glamour of the Western culture and the Polish political order where the magnates became the unrestricted rulers of the lands and serfs in their vast estates. In the 1569 Union of Lublin, the Ukrainian territories controlled by the Grand Duchy of Lithuania were transferred to the Crown of the Kingdom of Poland, and thus found themselves under the direct influence of the Polish culture and language. Ukrainian lands of Kyiv and Braclav voivodeship were rather sparsely populated and attracted a lot of settlers, mostly from Volhynia, but also from central Poland. One of the reasons was that serfdom was not introduced there. Among the settlers was also a petty nobility. Ruthenian, just like Lithuanian, nobility was attracted by the Polish culture, which at that time flourished. Many of them adopted the Polish language and customs, even converted to Roman Catholicism. Even for those who remained faithful to the Orthodox Church and Ruthenian language, Polish political identity became very important, as they were inspiring to be part of szlachta – a ruling, privileged elite. It was at that time when the concept of gente Ruthenus, natione Polonus (a Poles of a Rus' religion) was born.