A few years after earning his Ph.D. in Lwow under Twardowski, Jan Lukasiewicz (1878-1956) joined the faculty of the newly reopened University of Warsaw where he became, along with Lesniewski and his student Tarski, one of the founders of the Warsaw School of Logic. He did seminal research in many-valued logics, propositional calculi, modal logic, and the history of logic, especially concerning Aristotle´s syllogistic. He left Warsaw toward the end of World War II and found a new home at the Royal Irish Academy in Dublin where he continued his creative work.