 He had been a historian at the Polish Academy of Sciences since 1985 where he specialized in Polish medieval and communist era history, modern history and historical methodology.He finished his PhD in 1995 and was habilitated in 2000.He was a contributor to "Wielka Encyklopedia PWN" and "Polski Słownik Biograficzny" ("Polish Biographical Dictionary") and the author of more than 140 academic publications.