Nahum (Norbert) was born on January 11,1914 in Lemberg, Galicia (then part of the Austro-Hungarian Empire, now Lviv, Ukraine), to Shoshana and Dov Boris Chachkes. His parents were active Zionists. His father participated in the opening of the Technion in Haifa in 1924. The next year, they made aliyah and settled in Haifa, contributing a great deal to its building and development. His father was a construction engineer, and he was chosen to head the Union of Engineers and Architects in the city. His mother was the founder of the Women’s Labor Union of Haifa (later, WIZO). 

Nahum finished the Reali School and in 1932 joined Hagana Bet, which he left with the split of Tehomi. In 1938, he joined the British Army as an Arabic translator and as a communications officer for the Arab population during the “Arab revolt.” In 1940, he met Yair and told him that the armed resistance should wait until the end of the war. However, Yair convinced him that the revolution could not wait, and he joined Lehi. Yair gave him important intelligence mission, but after Yair’s murder, the links were severed. Yellin-Mor would renew these contacts in 1945. In the meantime, Nahum worked at the Dead Sea Works, overseeing the Arab and Druze employees; he was also responsible for communications with the British authorities in Jerusalem. In late 1945, he submitted to the central committee a program for psychological warfare against the British, under the cover of the “Jerusalem Mideast Union.”

This plan was approved, and the Jerusalem Mideast Union became famous as the lone meeting-place in Jerusalem where the leaders of the British Mandate could encounter Arab and Jewish notables. Nahum was the secretary of the Union, and he was the editor-in-chief of its periodical, in which monthly lectures were published. Most of the senior diplomats and religious officials were members of this Union. The deep connections forged at the Union were an important source of military and political intelligence for Lehi, and it also served as a conduit to disseminate information designed to cause tensions between the British and Americans. The Union remained in operation until the British left, and then Nahum joined Lehi forces in Jerusalem, serving as the deputy of David “Amihai” Gottlieb. He served in the battles in Jerusalem and the surrounding villages. After the Bernadotte assassination, Nahum was arrested with other Lehi members and held in Jaffa, Acre and Jalameh. He engaged in a hunger strike until the general clemency was granted. 

In late 1949, Nahum established a branch of an international industrial consulting company. He divided his time between Israel and Western Europe in order to manage the company.

In 1950, he married Ellen Luba, and they had two daughters, Karni Anat and Raya Mikhal. 

In 1977, after Begin became prime minister, Nahum suggested establishing an international trade syndicate which would operate a free-trade zone in the eastern Sinai. The plan went through many stages, but ultimately the assassination of Egyptian President Sadat put an end to the discussions.