Sejm during the Khmelnitsky Uprising. Election Sejm in Warsaw. 1648 r.
The Sejm was convened on August 1, and the pre-sejm sejmiks were held in August 1648. The proceedings began on October 6, 1648. The Speaker of the Sejm was elected Filip Kazimierz Obuchowicz, the Wojski (i.e. an officer whose duty was to maintain order in province while the nobility were engaged in military expedition abroad) of Mozyr. The march of Cossack troops heading for Lviv and Zamość after winning the Battle of Piławce influenced the functioning of the Sejm. So, the military matters and the organization of defense were dealt with. At the end of the Sejm proceedings on November 19, 1648, prince Jan Kazimierz Vasa was elected king, after his brother Karol Ferdinand withdrew his candidacy.
See: A. S. Radziwiłł, Pamiętnik o dziejach w Polsce [A memoir about the history of Poland], v. 3, 1637-1646, Translated and developed by A. Przyboś and R. Żelewski, Warszawa 1980, p. 113 et seq..; W. Czapliński, Sejm w latach 1587-1696 [Sejm in the years 1587-1696], in: Historia sejmu polskiego [History of the Polish Sejm], v. 1, Warszawa 1984, edited by J. Michalski, p. 217-299; E. Opaliński, Sejm srebrnego wieku 1587-1652. Między głosowaniem większościowym a liberum veto Sejm of the silver age 1587-1652. Between majority voting and liberum veto], Warszawa 2001. Legislation see: Volumina Constitutionum, v. 4, part. 1, prepared for printing by S. Grodziski, Marcin Kwiecień, K. Fokt, Foreword by W. Uruszczak, Warszawa 2015, p. 151-168.