the Caucasus. In 1618, the Thirty Years' War began. Czech Protestants were supported by German and Hungarian Protestants. The Hungarians asked the then Prince of Transylvania, Gabriel Bethlen, for help and declared their wish to unite Hungary with Transylvania. Bethlen had been appointed to the office after the Sultan's removal of Gabriel Báthory (ordered to the troops of Iskender Pasha in 1613). He was anti-Polish and a loyal Ottoman vassal and had aspirations to extend his rule to Moravia, Bohemia and Silesia. Polish hetman Stefan Żółkiewski warned Bethlen against joining the Protestant side and promised help against the Ottoman Empire; however, Bethlen answered that it was too late to change allegiances. When the fight was joined by Gabriel Bethlen on the Protestant side, his siege of Vienna threatened to extend Transylvanian rule (and thus Ottoman) to Bohemia and Silesia. 1619–20 Polish nobles (Szlachta) supported the Czechs (at least verbally) because the struggle of Czech and Hungarian nobles was viewed as a struggle of "free" nobility against absolutist monarchs. Nobles would not fight the Protestants, and the Sejm had even forbidden Sigismund III to send Polish armed forces as assistance to the Habsburgs. However, the king of Poland, Sigismund, was a devout Roman Catholic and a long time sympathizer of the Habsburgs. Additionally, some of the Polish magnates and szlachta hoped to get back some parts of Silesia in exchange for helping out the Habsburgs. During talks with Sigismund's son, Prince Władysław IV Waza, on his voyage to Silesia in mid-1619, Holy Roman Emperor Ferdinand II, promised to allow a temporary occupation of part of Silesia by the Poles, with the possibility of incorporating those areas into Poland at a later date. Some of the Piast (old Polish dynasty) dukes of Silesia also supported returning their lands to the Polish realm, especially given the attractive religious tolerance policy of the Commonwealth and the fact that the Polish western regions had been very peaceful and secure for a long time. Sigismund III decided to help the Habsburgs and privately hired an infamous mercenary group called the Lisowczycy (name took from their founder Aleksander Józef Lisowski), who were unemployed after the end of the wars with Muscovy (Dymitriads) and were plundering and terrorizing the entire region of Lithuania. Sigismund sent the Lisowczycy to aid the Habsburgs towards the end of 1619. In the end, Ferdinand did not agree to any permanent concessions in