Miłosz's riskiest underground wartime activity was aiding Jews in Warsaw, which he did through an underground socialist organization called Freedom. His brother, Andrzej, was also active in helping Jews in Nazi-occupied Poland; in 1943, he transported the Polish Jew Seweryn Tross and his wife from Wilno to Warsaw. Miłosz took in the Trosses, found them a hiding place, and supported them financially. The Trosses ultimately died during the Warsaw Uprising. Miłosz helped at least three other Jews in similar ways: Felicja Wołkomińska and her brother and sister.