Siman-Tov Ganeh was born in the Old City of Jerusalem to a Georgian-Jewish family, son of a member of the Jewish Battalions and a volunteer in the British army's Expeditionary Force during the Second World War. When the 1936–1939 Arab revolt broke out, his family was forced to leave the Old City and move to Zikhron Moshe. As a boy he worked in a cigarette factory, and in 1941 his father fell captive in Crete. He also served in the Royal Navy, and served on supply ships. In April 1946, he was discharged and worked as a taxi driver shortly before joining the Lehi underground movement.