The day began with shootings near the church in Ain al-Rummaneh, where Pierre Gemayel was attending a consecration; his bodyguard Joseph Bou Assi was killed. In the early afternoon Kataeb militiamen fired on a bus returning to Tal al-Za'tar from a rally of the Arab Liberation Front. Most historians count 27 dead (Hanf, Fisk, de Clerck and Malsagne: 27 of 35 passengers); Traboulsi gives 21 and Ménargues 31. According to de Clerck and Malsagne the bus carried Palestinians and Lebanese in equal numbers, all men. Fighting spread that evening across the suburbs of Beirut.

After several days of fighting (Hanf; four, says Traboulsi), Pierre Gemayel gave up to the police two militiamen implicated in the Ain al-Rummaneh shooting. Early Syrian mediation failed to stop this round, which de Clerck and Malsagne end with a cease-fire on 16 May 1975; no book confirms a truce on 15 April.

Parliament used the truce to amend Article 73 of the constitution so that Frangieh's successor could be elected early: on 9 April according to Hanf, 10 April according to Yara El Khoury. The truce had coincided with the arrival on 31 March of the US envoy Dean Brown.

Traboulsi's chronology puts the Syrian-PLO accord to restore order in Beirut on 11 April. Around 9 April Syrian army tanks entered the Bekaa at Anjar, Judaydat Yabus and Bayadir al-Adas (Traboulsi), some forty in all according to Yara El Khoury, as Saiqa fighters set about ending the siege of Zahleh.

Sami al-Khatib took over the ADF from Ahmad al-Hajj, who never won Syria's trust, and led it until 1983.

By now Syria was fighting on the Palestinians' side. Hanf says the clashes ended once the Arab Deterrent Force's Saudi and Sudanese contingents deployed between Chiyah and Ain el-Remmaneh.

Neither parliament nor president could enforce the resolution, Hanf notes. The 74 deputies in attendance passed it without dissent: it reserved arms to the legitimate Lebanese forces, told the Palestinians and 'other parties' to end armed action, and applied Lebanese law to all on Lebanese soil.

De Clerck and Malsagne and Picard agree that Haddad declared his 'State of Free Lebanon' at Marjayoun on 18 April 1979, in reaction to the army being sent towards the UNIFIL area under the March 1979 defence law; de Clerck and Malsagne put its size at 250 square kilometres and call it entirely reliant on Israel. Hanf has Haddad's troops stopping the battalion; de Clerck and Malsagne and Picard, Israeli aircraft bombing it; Fisk, Israel letting its militia shell it. Traboulsi dates Haddad's break to his Army of Free Lebanon of June 1976, Ménargues to a secession at the end of 1977. Hanf adds that once Haddad had lost his rank and been dismissed in disgrace, Israel paid his men.

Fisk: violating the UN's agreements with Israel, Haddad's militia set up positions inside the UNIFIL zone in spring 1980, beside At-Tiri, near Beit Yahoun and at ruined Rashaf, where it parked a Sherman tank reached by a road built with Israeli help.

Fisk: in the April 1980 fighting at At-Tiri, Haddad's gunmen killed Private Stephen Griffin of the Irish UNIFIL battalion and UN troops killed a militiaman, whose death two other Irish soldiers later paid for. The militia also held the coastal strip between the French unit and Naqoura and shot at helicopters.

Hanf sees the Iran–Iraq war of September 1980 as already being fought earlier in Beirut's suburbs: Amal and the Iraqi-backed Arab Liberation Front clashed there despite repeated ceasefires, and the fighting spread south, where a dozen villages were contested until mid-1982. De Clerck and Malsagne list the Iraqi Baath among Amal's adversaries.

Historians date the battle of Zahleh from this day, when Lebanese Forces fighters beat off a Syrian attack on the town and a siege of some 90 days began. Ménargues says Syrian heavy guns killed 50 and wounded over 200 that day in Zahleh and the Christian zone north of Beirut.

Ménargues dates a day of intensive shelling of Zahleh, with about twenty dead, to 6 April.