What events started the Lebanese Civil War in 1975?

The Lebanese Civil War is typically dated to April 13, 1975, when Phalangist forces attacked a bus carrying Palestinians to a refugee camp at Tell al-Zaatar near Beirut. This violent incident escalated existing tensions into a broader conflict between the Phalangists and the Lebanese National Movement (LNM), a coalition of leftists and Muslims who supported the Palestine Liberation Organization (PLO).12

The outbreak of war was the culmination of years of growing instability. By the mid-1970s, Lebanon’s delicate political and confessional balance had begun to unravel due to several factors:

• Socioeconomic Polarization: Rapid urbanization and uneven development created a "poverty belt" of marginalized rural migrants around Beirut, fueling social alienation.3
• Palestinian Presence: Following their expulsion from Jordan, the PLO established a significant presence in Lebanon, effectively operating as a "state within a state" and attracting retaliatory Israeli raids.34
• State Weakness: The Lebanese government proved increasingly unable to maintain a monopoly on force, leading various political and sectarian factions to organize and arm their own militias.4
• Political Crisis: The presidency of Suleiman Franjieh was marked by corruption and an inability to manage these competing forces, prompting the Phalangist militia to begin confronting Palestinian groups directly.4