This violence was exacerbated by an influx of some 3,000 PLO militants who had fled Jordan following the defeat of Palestinian groups to Jordanian forces during the Black September conflict; the Palestinian political cause began to regroup in southern Lebanon and re-shifted the focus of its attacks to Israeli targets, and did so via the Israel–Lebanon border.

Israel responded to Palestinian attacks from Lebanon with extensive air raids against PLO bases of operations.

[10] On that day, 11 Palestinian Fatah members led by the 18-year-old female fighter Dalal Mughrabi travelled from Lebanon to Israel, where they killed an American tourist at a beach before hijacking a bus on the Coastal Road near Haifa; the group later also hijacked a second bus that was bound for Tel Aviv.

The operation began with air, artillery, and naval bombardment, after which IDF infantry and armor forces, comprising about 25,000 soldiers, entered south Lebanon.

The Israelis first captured a belt of land approximately 10 kilometers deep, by launching a ground attack on all PLO positions along the Lebanese border with Israel.

[13] Many Lebanese civilians were killed by heavy Israeli shelling and air strikes, which also caused extensive property damage and internal displacement.

[13] According to Augustus Richard Norton, professor of international relations at Boston University, the IDF military operation killed approximately 1,100 people, most of them Palestinian and Lebanese.

[15] Carter's administration prepared to notify Congress that American weapons were being used illegally, which would have resulted in military aid to Israel being cut off.

[15] The American consul in Jerusalem informed the Israeli government of their plans and, according to Carter, Prime Minister Begin said that the operation was over.

[14] The PLO leadership finally ordered a ceasefire on 28 March 1978, after a meeting between UNIFIL commander General Emmanuel Erskine and Yasser Arafat in Beirut.

Continued attacks in Israel from the Lebanese based PLO[18][19][20] culminated in a second Israeli invasion in 1982 resulting in a flare-up that persisted over the next decade.

[22] Hezbollah's claim that Israel has not fully withdrawn (see Shebaa Farms) was explicitly rejected by the UN's Secretary-General's report which led to Resolution 1583.