Under the leadership of Jumblatt, the PSP was a major element in the Lebanese National Movement (LNM) which supported Lebanon's Arab identity and sympathized with the Palestinians. It built a powerful private army, which proved to be one of the strongest in the Lebanese Civil War of 1975 to 1990. It conquered much of Mount Lebanon and the Chouf District. Its main adversaries were the Maronite Christian Phalangist militia, and later the Lebanese Forces militia (which absorbed the Phalangists). The PSP suffered a major setback in 1977, when Kamal Jumblatt was assassinated. His son Walid succeeded him as leader of the party.