On the morning of September 16, the Operations Command of the Northern Command and the Phalangist officers discussed how the Christian forces would operate within the refugee camps, in coordination with the IDF. During the course of the meeting, the IDF stressed that the civilian population was not to be harmed. In the afternoon, the Christian forces crossed the IDF lines into the refugee camps in order to confront the unknown number of Palestinian terrorists who were apparently based in the camps.
Shortly thereafter, the Phalangists began indiscriminately killing camp residents, in retaliation for Gemayel’s assassination. The victims included women, children, and babies. According to IDF intelligence estimates, approximately 700-800 Palestinian refugees died.
On the morning of September 18, the Phalangists exited the camps, and the IDF took control of the area. That same night, the Lebanese Health Ministry and Lebanese soldiers began removing the hundreds of bodies for burial. According to witnesses, who later testified, numerous atrocities were uncovered, including rapes, desecration of corpses, and the destruction of houses with their residents still inside.
Despite the IDF’s assessment that a massacre might occur, and notwithstanding the unambiguous reports which reached Defense Minister Ariel Sharon and Chief of Staff Rafael Eitan, the IDF did not prevent the massacre. By the night of September 16, the IDF had begun to receive reports of the killings, and reports reached several policy makers a few hours later. Nonetheless, no action was taken to stop the killings.
The massacre reverberated throughout Israel. Peace Now organized a massive rally in Tel Aviv, and then Prime Minister Menachem Begin was pressured to establish an investigative committee. On September 29, Begin launched a state commission, headed by Supreme Court Chief Justice Yitzchak Kahan. Supreme Court Judge Aharon Barak and Major-General (res.) Yona Efrat were also commission members.
On February 7, 1983, the Kahan Commission submitted its findings. The Phalangists were given full blame and responsibility for the massacre. Nonetheless, the commission noted several flaws and failures on the part of some Israeli political and military leaders.
With respect to Prime Minister Begin, the commission neither made personal recommendations nor determined that he had any direct responsibility. However, the commission stated that, “Begin’s noninvolvement in the entire issue charges him with a certain amount of responsibility.”
With respect to Defense Minister Ariel Sharon, the commission determined that he was responsible for ignoring the possibility of a massacre, both by approving the Phalangists’ entrance into the camps and by not lining up resources to prevent the possibility of a massacre. According to the commission, these omissions indicated that the defense minister had not fulfilled his duties. Thus, the commission recommended that he be removed from his position, and, in accordance with these findings, Begin did in fact dismiss Sharon.
With respect to Chief of Staff Rafael Eitan, the commission declared that he had neither taken the necessary steps to prevent the danger of a massacre nor tried to stop the massacre once it had started. As such, Eitan had not fulfilled his responsibilities as chief of staff. However, since he was already about to conclude his term as chief of staff, the commission did not recommend that he be relieved of his duties.
Yehoshua Sagi, head of the Intelligence Branch, was found guilty of indifference and disregard with respect to the Phalangists’ potentially dangerous activities. Thus, the commission recommended that, “Major-General Yehoshua Sagi should not continue in his position as head of the Intelligence Branch.” This recommendation was accepted, and Sagi was dismissed.
In addition, the commission recommended that Amos Yaron, the commander of the IDF troops in Beirut, be transferred to a non-commanding position for three years.
With respect to OC Northern Command Amir Drori, the commission determined that he "…was charged with many difficult and complicated tasks during the week the IDF entered West Beirut, missions which he had to accomplish after a long period of difficult warfare. He took certain measures for terminating the Phalangists' actions, and his guilt lies in that he did not continue with these actions. Taking into account these circumstances, it appears to us that it is sufficient to determine the responsibility of Major General Drori without recourse to any further recommendation".
Drori continued to serve in his post as Northern Command general until December 1983, and then went to the United States to study. In February 1985, he was appointed head of the combat corps headquarters (later known as the GOC Army Headquarters), and in September 1986, was appointed deputy chief of staff.