Karameh, withdrawing only under Jordanian military pressure. This conflict culminated in Jordan's expulsion of the PLO to Lebanon in July 1971. Black September The PLO suffered a major reversal with the Jordanian assault on its armed groups, in the events known as Black September in 1970. The Palestinian groups were expelled from Jordan, and during the 1970s, the PLO was effectively an umbrella group of eight organizations headquartered in Damascus and Beirut, all devoted to armed struggle against Zionism or Israeli occupation, using methods which included direct clashing and guerrilla warfare against Israel. After Black September, the Cairo Agreement led the PLO to establish itself in Lebanon. Lebanon and the Lebanese Civil War In the late 1960s, and especially after the expulsion of the Palestinian militants from Jordan in Black September events in 1970–1971, Lebanon had become the base for PLO operations. Palestinian militant organizations relocated their headquarters to South Lebanon, and relying on the support in Palestinian refugee camps, waged a campaign of attacks on the Galilee and on Israeli and Jewish targets worldwide. Increasing penetration of Palestinians into Lebanese politics and Israeli retaliations gradually deteriorated the situation. By the mid-1970s, Arafat and his Fatah movement found themselves in a tenuous position. Arafat increasingly called for diplomacy, perhaps best symbolized by his Ten Point Program and his support for a UN Security Council resolution proposed in 1976 calling for a two-state settlement on the pre-1967 borders. But the Rejectionist Front denounced the calls for diplomacy, and a diplomatic solution was vetoed by the United States. In 1975, the increasing tensions between Palestinian militants and Christian militias exploded into the Lebanese Civil War, involving all factions. On 20 January 1976, the PLO took part in the Damour massacre in retaliation to the Karantina massacre. The PLO and Lebanese National Movement attacked the Christian town of Damour, killing 684 civilians and forcing the remainder of the town's population to flee. In 1976 Syria joined the war by invading Lebanon, beginning the 29‑year Syrian occupation of Lebanon, and in 1978 Israel invaded South Lebanon in response to the Coastal Road Massacre, executed by Palestinian militants based in Lebanon. The population in the West Bank and Gaza Strip saw Arafat as their best hope for a resolution to the conflict. This was especially so in the aftermath of the Camp David Accords of 1978 between Israel and Egypt, which the Palestinians saw as