Born in Jerusalem during the Mandate era as Meir Pilevsky, Pa'il served in the Palmach between 1943 and 1948, after which he became a Brigade commander in the new Israel Defense Forces. He also headed the Central Officers School and the Department of Military Theory for the General Staff. He left the IDF in 1971.
Pa'il studied history and Middle Eastern studies at Tel Aviv University, later gaining a doctorate in military and general history.
He was elected to the Knesset in the 1973 elections on the Moked list, and was the party's only representative in the Knesset. The party merged with several others to form the Left Camp of Israel prior to the 1977 elections. The new party won two seats, which were rotated between five party members including Pa'il. However, they failed to win any seats in the 1981 elections and Pa'il did not reappear in the Knesset.