Because of the limits imposed by the Isaraeli cabinet, the IDF implemented its attack in increments, neither openly recognizing nor acknowledging its destination and objectives. Had it been ordered from the outset to secure Beirut, it could have done so in an effective and efficient manner. Instead, the IDF advance unfolded in an ad hoc and disorganized fashion, greatly increasing the difficulty of the operation.
When IDF ground forces crossed into Lebanon on June 6, they pursued a battle strategy that entailed a three-pronged attack conducted by five divisions and two reinforced brigade-size units. On the western axis, two divisions converged on Tyre and proceeded north along the coastal road toward Sidon, where they were to link up with an amphibious commando unit that had secured a beachhead north of the city. In the central sector, a third division veered diagonally across southern Lebanon, conquered the Palestinian-held Beaufort Castle, located a few kilometers southwest of Marj Uyun, and headed west toward Sidon, where it linked up with the coastal force in a classic pincer movement. The IDF advanced rapidly in the first day of the war, bypassing and enveloping pockets of PLO resistance. Most PLO military officers fled, abandoning their men, who split into small roving guerrilla bands. Moreover, it became clear that the PLO was fighting alone against the Israeli onslaught. The Shia Amal guerrillas had been ordered by their leaders not to fight and to surrender their weapons if necessary. South Lebanon's Shias had long suffered under Palestinian domination, and Shia villagers welcomed the advancing Israelis by showering them with rice and flowers. This traditional form of homage, later repeated by the Druze and Christian populations, lent credence to the Israeli claim that it was "liberating" Lebanon.
But Palestinian resistance proved tenacious, particularly in the sprawling refugee camps in the vicinity of Tyre and Sidon (see fig. 4,). Staging hit-and-run operations and fighting in house-to- house and hand-to-hand combat, the Palestinians inflicted a high number of casualties of the IDF and impeded the progress of the Israeli advance. The IDF was further hampered because the refugee camps were inhabited by large numbers of civilian noncombatants who harbored the Palestinian fighters. Although the IDF made significant initial efforts to evacuate the civilians, it ultimately resorted to saturation bombing to subdue the camps. Palestinian resistance was especially fierce in the Ayn al Hulwah camp near Sidon, where several hundred Palestinian fighters fought to the last man, delaying the IDF advance for seven days. After the camp was leveled, the IDF stood poised to move against Beirut.
Two days later in eastern Lebanon, two divisions thrust directly north on parallel courses into Syrian-held territory with the mission of severing the strategic Beirut-Damascus highway. On June 8, the IDF evicted the Syrian Army from Jazzin and proceeded north. A brigade of Syrian commandos, however, ambushed the Israeli column in the mountainous terrain near Ayn Zhalta, approximately five kilometers short of the highway.
The IDF could not proceed further against the entrenched Syrian positions without close air support, but Syria's air defense systems threatened Israeli control of the skies. On June 9, the Israeli cabinet gave permission for an air raid against the Syrian antiaircraft missile batteries in the Biqa Valley. The Syrians, caught by surprise, sustained severe losses; of the nineteen missile batteries, only two were left intact by the Israeli attack. The Syrian Air Force made a desperate bid to protect the air defense system by sending up scores of interceptors and fighters, resulting in what both sides described as the biggest air battle in history, with over 200 aircraft engaged in supersonic dogfights over a 2,500 square kilometer area. The Israeli Air Force shot down twenty-nine Syrian aircraft that day (and later about fifty more) without a single loss. The devastation of the Syrian air defense system and the decimation of the Syrian Air Force provided the IDF with total air superiority in Lebanon and left the Syrian infantry exposed to air attack.
For three more days, the IDF mauled Syria's First Armored Division. The IDF was still stalled short of the Beirut-Damascus highway, but it was on the verge of breaking through the last line of Syria's defense. Bowing to political pressures, however, on June 11 Israel and Syria agreed to a truce under United States auspices.
Data as of December 1987