Active in the Zionist movement throughout the 1930s, he was sent with the Polish army-in-exile to Palestine (1942), where he joined the militant Irgun. On the creation of Israel (1948) the Irgun regrouped as the Herut (Freedom) Party and elected Begin as its head. He was leader of the Opposition in the Knesset (Parliament) until 1967, when he joined the National Unity government. In 1970 he served as joint chairman of the Likud (Unity) coalition, and after its electoral victory in 1977 became Prime Minister (1977–83). He negotiated a peace treaty with President Sadat of Egypt at Camp David, but remained opposed to the establishment of a Palestinian state.