Phalangist forces killed twenty-six Fatah trainees on a bus in April 1975, marking the official start of the 15-year-long Lebanese civil war. Later that year, an alliance of Christian militias overran the Palestinian refugee camp of Karantina killing over 1,000 civilians. The PLO and LNM retaliated by attacking the town of Damour, a Phalangist and Tigers (Ahrar) stronghold, killing 684 civilians. As the civil war progressed over 2 years of urban warfare, both parties resorted to massive artillery duels and heavy use of sniper nests, while atrocities and war crimes were committed by both sides.