Closely allied with the Al-Mourabitoun, the PNO/NLA joined the Lebanese National Movement (LNM) in April 1975, playing a somewhat significant role in the controversial siege of the Christian coastal town of Damour alongside the Al-Mourabitoun, the PLO and Palestine Liberation Army units on 20–22 January 1976, and later took part in the 'Spring offensive' held in March that year on the Mount Lebanon region. Forced to go underground during the June 1982 Israeli invasion of Lebanon when the Israeli Defence Forces (IDF) occupied Sidon, the PNO/NLA re-formed in the wake of the Israeli pull-out from southern Lebanon in March–April 1985, and fought alongside the Palestinians at the battles for Kfar-Fallus and Jezzine against the Israeli-backed South Lebanese Army (SLA). Simultaneously, they joined in a Syrian-backed coalition with the Druze Progressive Socialist Party (PSP), the Sunni Al-Mourabitoun and the Shi'ite Amal Movement, which defeated the Christian Lebanese Forces (LF) attempts to establish bridgeheads at Damour and Sidon.