In 1942 Nahman went to Budapest in order to learn to be an electrician and made contact with other members of his movement. After the Germans occupied Hungary on 19.3.1944, he became an underground activist and received forged documents from Vili Eisikovics. Following Tzvi Goldfarb’s instructions, Nahman engaged in obtaining Aryan documents, smuggling Jews into Romania and building bunkers. In August 1944 he tried to cross the border into Romania. He was caught, interrogated and put on a deportation train but managed to escape while the train was near Budapest. Nahman arrived in the underground center of the movement in Baross Street. Donning a Levente uniform, he ran various errands mainly supplying food to the bunkers. He was arrested again and sent to the prison on Margit Boulevard. He was transferred to the border with Austria where he was forced to do bomb clearing. Nahman was released by the Red Army at the end of March 1945.
He made aliya in 1946 and was one of the founders of Moshav Beit Hanina (1950).