Yaakov, son of David and Sarah, was born in 1917 in the Łomża District of Poland, between Bialystok and Warsaw. He and his family made aliyah and settled in Tel Aviv. His father was one of two kosher butchers in the city. Yaakov started studying in cheder, and when they moved to Raanana, he went to elementary school there (he was one of only five students).
The father could not find work, so in 1925, he moved to the United States, while the family stayed in Israel. Yaakov started studying in Nordia Gymnasium, but due to an illness, he left and continued at the Montefiore Gymnasium. He did not complete his studies there either, and he continued with night classes.
When he reached the age of bar mitzva, he bought a pistol, worried about altercations with the Arabs. At age fifteen, he joined Brit HaBiryonim, and he was active in it. While at Montefiore, he joined IZL. The conflict between the two organizations caused a great deal of strife. As World War II broke out and Lehi split off from IZL, Yaakov (who was in charge of the youth organizations and political movements of the Intelligence Services Division, Meshi) transferred all of the materials he had assembled to Lehi.
He was a radio technician by profession, and he built transmitters both for the British Army and for the Hagana. He was in close contact with Hagana members, even though he was not a member of that organization (he was already in Lehi). When Deputy Superintendent Shlomo Schiff and Inspector Nathan Goldman were killed by a rooftop bomb set by Lehi, Yaakov’s identity was revealed and he was seized by the Hagana. He was kept for a number of weeks in an orchard in Sharon, where he was interrogated, tortured and beaten. The day after his release, he was arrested, transferred to Jaffa Prison, then to Mizra and Latrun. On 19 October 1944, he was sent with the first group of 251 detainees to Africa. He was held at Sembel (near Asmara, Eritrea), Carthago (Sudan), back in Eritrea and finally in Gilgil (Kenya). He was returned to Israel on 12 July 1948, after six-and-a-half years of detention in Israel and abroad.
Yaakov enlisted in the IDF. He served in the Artillery Corps, where he was made director of its laboratory.
In 1951, he married Adele Schaeffer and they had three children. After his demobilization, he set up a cooperative for installing telephones, and later he worked as a civilian employee of the Israeli Air Force. Later still, he moved to Haifa, where he was given an apartment as the director of the equipment department of what would eventually become the Chemical Research Center of Israel Chemicals Limited Industrial Products Group. He worked there until he retired.
Yaakov was a researcher and writer. He wrote a book, The Riddle of the Dome of the Rock. He also studied the Hebrew language and published articles on the subject.
Yaakov collected a large number of archeological artifacts from Rushmiyeh, which he donated to the Israel Museum.