Ya’acov was born  August 21, 1921 in Vilnius Poland, to his father Nahum and  mother Dina, daughter of Rabbi Eliya Halperin. He  graduated from “Tushiya” Hebrew High School. At age 13 he joined Beitar.  On September 2, 1938 he made Aliyah alone. An entry permit was sent by his family in Haifa. Ya’acov’s  entire family perished in the holocaust; Aliyah had saved his life. On arrival he joined Etzel, instructed  youth and headed Beitar  Kfar-Saba. He worked at the Kfar-Saba orchards, and agricultural work in Magdiel. In 1939, within Etzel activities countering non-reaction, he was involved in an operation in the Sharon area. After the split in Etzel he joined Lehi, changing his name to Avneri. He participated in putting up info-bulletins and surveillance. After Lehi’s  attempted assassination of Yair’s murderer, Major Morton, he was arrested in Haifa May 1942, and jailed in Mizra and Latrun Prison Camps. Ya’acov was exiled to Africa with the first batch of 251 prisoners. He was held at  Simbal prison Camp in Eritrea, Carthago in Sudan, back to Eritrea and lastly  Gilgil Camp Kenya. He participated in the great escape of 54 exiles from  Eritrean Prison Camp  June 1946, through two escape tunnels dug by the prisoners. He was caught and returned. After Independence was declared, he was returned with the remaining Kenyan exiles, having done six years’  prison. Back in Israel, he underwent training in Kibbutz Afikim, for establishing the new outpost-settlement “Neve-Yair”. He fought in the War of Independence . In the course of a battle, a bullet injured his abdomen and  kidney, going out through his back. This left him 55% handicapped, a disabled war veteran. In 1952 he married Eva Radumilski. Their eldest son Yair was born 1956, then  their daughter Arela (Reli) 1958. They had four grandchildren.

He became 100% disabled after a failed operation, and was forced to retire. Highly intelligent, Ya’acov had  vast knowledge of Hebrew Linguistics, Judaism and Classical Music. He educated his children in the Zionist beliefs dear to his spirit. Ya’acov passed away January 11, 1996. He was buried in the Lehi section of  Yarkon Cemetery.