Complex sentence: Marcin Urynowicz is a Polish historian, writer, and panelist associated with the Institute of National Remembrance research department, and specializing in World War II history of Poland with focus on Polish-Jewish relations and the Rescue of Jews by Poles during the Holocaust.
Split into simpler sentences: Marcin Urynowicz is a Polish historian, writer, and panelist associated with the Institute of National Remembrance research department. Urynowicz specializes in World War II history of Poland with a focus on Polish-Jewish relations and the Rescue of Jews by Poles during the Holocaust.