 Musawi was a "chemistry teacher turned militia commander" who became the deputy head and official spokesman of the Amal movement/party/militia, Lebanon's largest Shi'ite movement.On June 21, 1982 he defected from Amal to start the Islamic Amal splinter group, operating out of Baalbek, Lebanon.Musawi disapproved of Amal leader Nabih Berri's participation in the first session of the six-man Lebanese National Salvation Committee, his acceptance of "U.S. diplomatic efforts to end the Israeli siege of West Beirut, which was also Amal's strong hold,"  and his opposition to the pledging of pan-Islamic allegiance by Amal to Iranian Revolutionary Islamist leader Ayatollah Khomeini.