Yaacov was born on January 16,1924 in Lublin Poland to Bracha and Yehushua. His father was a religious Jew. The family made Aliyah 1938 and settled in southern Tel-Aviv. Due to their harsh financial situation, Yaacov had to begin working young. To complete studies, he attended evening classes. He was a  religious youth-movement member and  joined  Lehi 1943, out of desire to expel the British from the Land of Israel. Yaacov was known for being coolheaded, for his intelligence and inventiveness, qualities which assisted his underground work. He was among the founders of Lehi’s Technical Department, which created explosive material used by Lehi for many sabotage activities, including blowing up the Jaffa “Saraya” building. On the  first night of the Hebrew Revolt Movement, November 1,1945  Yaacov was severely injured during the attempt to blow up the Haifa refineries. An explosive device  brought into the refinery area in advance , detonated before it’s designated time. Moshe Bar-Giyora was killed, other members were injured. Yaacov escaped, but his ID card remained at the scene. He was transferred to a Haifa hospital. Much shrapnel remained in his body throughout life. From that day he had to hide  and worked from within the Lehi organization. Yaacov participated in many operations: confiscation of cash/jewellery to fund underground activities; helping free Dr Israel Eldad, from Dr. Troy’s Jerusalem clinic. He participated in attacking the British Airport near Kfar Sirkin, where ten ‘Spitfire’ combat planes were blown-up.

During a joint attack with Etzel, attempting to rescue prisoners from Jerusalem Central Prison, he remained stranded an entire night at the Fire Station adjacent to the prison. With inventiveness he prevented local Arabs from turning him in, threatening to detonate a  matchbox, which was actually empty. After establishment of the State, he joined the IDF’s 8^th Brigade. He fought in its 89^th Battalion and participated in the Operation ‘Dani’ battles, liberation of the Negev and the south, and the conquest of Uja-el-Hafir.

After the war he married Esther Mechtinger, underground comrade, established a  solar water-heater factory, and acquired a house in Tzahala. They had a daughter and son, Orna and Tamir, plus six grandchildren. One grandchild is named Dan, honoring Yaacov’s nom-de-guerre.

Yaacov passed away on September 19,1987 at 63, and was laid to rest at Ramat-Hasharon Cemetery.