In 1943, he arrived in Eretz Israel aboard an illegal immigrant ship which was intercepted by the British, and was interned at Atlit with the other passengers. He remained there until the prisoners were freed by the Palmach (the Haganah elite unit)(October 9, 1945), moved to Natanya, and shortly afterwards joined the Irgun.
He was assigned to the Fighting Force and took part in several operations: the assault on the army recreation camp at Natanya and the sabotaging of bridges and railroad lines.
In the Acre prison-break (May 4, 1947), he was assigned to the covering unit, together with Avshalom Haviv and Meir Nakar. They fought to the last bullet and finally were captured by the British. About three weeks later the three Irgun fighters were tried and sentenced to death. On July 29, 1947 Yaakov Weiss was hanged at the Acre prison, together with his comrades: Avshalom Haviv and Meir Nakar. Weiss was 23 when he went to the gallows.