 Complete the following phrase:  The M-50 Continentals were retired by 1972. The M-50 Cummins and M-51 were gradually phased out in late 1970s to early 1980s. During the Lebanese Civil War, some 75 M-50s were given as aid to the Israeli-supported Lebanese Christian militias  Kataeb Regulatory Forces 19, Tigers Militia 20, Guardians of the Cedars 1, the Lebanese Forces 40, and the South Lebanon Army 35  in 1976; two tanks were later captured by the Palestine Liberation Organization PLO, which employed them in the defense of West Beirut during the 