Bernard Mark was born Ber or Berl Mark to a Jewish family in Łomża, Poland, then part of the Russian Empire. In 1932, he graduated with a law degree from the University of Warsaw. During his student days, he joined the Communist Party of Poland and published articles in Polish and Yiddish in the Jewish press. He became the editor of the Communist newspaper Der Frajnd (The Friend) in 1934. In 1937, he married Esther Goldhase, a teacher and fellow Communist activist. Before World War II, he wrote a two-volume book, Geszichte fun di socjale bawegungen in Pojln (History of Social Movements in Poland). From 1942 to 1943, he worked for the Jewish Antifascist Committee and the Union of Polish Patriots in the USSR. There he first published his work The Uprising in the Warsaw Ghetto in pamphlet form. After the war, he returned to Poland, where in 1949 he became director of the Jewish Historical Institute in Warsaw, a position he held until his death. During his tenure, the Institute's publications, the Biuletyn and Bleter far geshikhte, published important studies by Artur Eisenbach, Tatiana Berenstein, Adam Rutkowski, Szymon Datner, Danuta Dąbrowska, Ruta Sakowska, and others about the history of the Holocaust on Polish soil.