Jewish Combat Organization
During World War II, Betar members, including former Polish Army officers, founded "Żydowski Związek Wojskowy" (ŻZW; "Jewish Military Union"), which fought in the Warsaw Ghetto Uprising. Mordechai Anielewicz, the head of the other major uprising group, "Żydowska Organizacja Bojowa" (ZOB; "Jewish Combat Organization"), also gained his military training in Betar. He was the secretary of the prominent Betar Warsaw organization in 1938. He left it to join and quickly take leadership of the left-wing Zionist Hashomer Hatzair group in Warsaw.