Yaakov joined the “Beitar” movement during his studies in Munkács. In 1944 he moved to Budapest and was a prominent activist of his movement in the underground. He saved Jews from the gathering places for deportation by giving them forged documents. Under his influence and with his help, a group of comrades from the movement arrived in Budapest and joined the underground activities of “Beitar”. Yaakov left Hungary in June 1944 on the train of the Relief and Rescue Committee. He made aliya in 1945 and took part in the armed operations against the British mandate in Palestine. He was caught and sentenced to death. He refused to sign an appeal for pardon and was executed in July 1947.