In 1944 was appointed commander of Delek (the intelligence service) and made a member of the General Headquarters. During the "Hunting Season", was kidnapped by the Haganah, and interrogated at length under severe torture. He was detained for six months, and released when negotiations began for the establishment of The United Resistance.
After release, he was sent to Europe to organize the Irgun branches there. He was arrested in Italy after the explosion at the British Embassy in Rome and two months later was expelled from Italy and moved the Irgun headquarters in Europe to Paris. In the three years he spent in Europe, he organized and expanded the Irgun branches in various countries.
Was an active participant in the dispatch of the Altalena.
After the state of Israel was established, he returned to Israel and changed his name to Eliezer Yaakov Tavin. Graduated from the Hebrew University with a Ph.D. in philosophy and history. Was a member of the Zionist Executive and Director of the Department for Education and Culture in the Diaspora of the Jewish Agency.
Published a book "The Second Front - The Irgun in Europe 1946-1948" (Ron, 1973).