With 43 seats, the Likud still required the support of other parties in order to reach a parliamentary majority that would enable it to form a government under Israel's proportionate representation parliamentary system. Though able to form a narrow coalition with smaller Jewish religious and ultra-orthodox parties, Begin also sought support from centrist elements in the Knesset to provide his government with greater public legitimacy. He controversially offered the foreign affairs portfolio to Moshe Dayan, a former IDF Chief of Staff and Defense Minister, and a prominent Alignment politician identified with the old establishment. Begin was sworn in as Prime Minister of Israel on 20 June 1977. Dash eventually joined his government several months later, thus providing it with the broad support of almost two thirds of the Knesset. While Prime Minister, Yehuda Avner served as Begin's speech writer.