Al Hajj fought against the Israeli occupation in South Lebanon and was then transferred to head positions north of the Litani during the 1980s. From 1988 to 1989 he fought, under the leadership of Prime Minister General Aoun, against Syrian forces assaulting the "free zones" of West Beirut during the Lebanese Civil War, he also battled the Lebanese Forces militia. In addition, General Hajj, led the Lebanese Army operation in Dinnieh in 2000. He gained recognition as a brilliant commander during the 15-week operation against Fatah al-Islam in Nahr al-Bared camp northern Lebanon during Summer 2007. He was second in command in the Lebanese army and would have been a contender to replace General Sleiman in the event the latter was elected president. . Hajj was promoted to the rank of major general after his killing.