To destroy the basis of Palestinian nationhood, Israel had to crush every manifestation of civil society, political and military development among the Palestinians living in border areas and miserable refugee camps, from 1949 onward. Repeated incursions into Jordan, including the bombing of Irbid, and the ethnic cleansing of one and a half million people from the Suez Canal area in 1970, was a logical corollary of this. The Hashemite kingdom of Jordan had been the Zionists' key ally in the originary purge of 700,000 Palestinians that enabled the Israeli state to come into being. It was a major host of refugee populations, tightly controlling their movements and environment on Israel's behalf. Israel foresaw, however, that if local populations sympathised with the refugees, they had a political problem on their hands. So, their repeated attacks were in part an endeavour to turn local populations against the Palestinians, frightening them enough to pressure the Jordanian government into acting against the refugees. After a series of massacres by the Jordanian state, refugees aligned to the PLO were driven into Lebanon, right into the middle of a brewing civil war between, loosely, left-wing and Islamic groups on the one hand, and right-wing Maronite groups on the other. The PLO sought to avoid being dragged into that war, but when Phalangists started, using Israeli-supplied weaponry, to attack Palestinians, the PLO joined with local leftist forces. Israel was intervening directly long before its invasion, its actions including the napalming of a refugee camp, killing 200 people. By 1982, under the Likudnik Prime Minister and veteran of 1948, Menachem Begin, Israel had opted for open conquest.

Israel had a number of interests in the war. They wanted to crush the PLO, to align themselves with the right-wing Maronite forces with whom they believed they had a natural alliance (and it would make sense geopolitically in terms of opposing both left-wing and Islamist movements), and to extend their border somewhat to the north. Just as was witnessed during Israel's assault on Lebanon in 2006, Zionism is ideologically committed to the idea that the territory at least up to the Litani river belongs to Israel. The attempted ethnic cleansing of southern Lebanon during the invasion took the form of dropping leaflets from 20 June 2006 on civilian areas, ordering all Lebanese to evacuate for their own safety - and then dropping bombs on them as they fled. On 23 June 2006, Israel explicitly acknowledged that it intended to set up a military administration in the entire area south of the Litani. Whether or not international opinion (ie, that of the US and its allies) would accept this, it would count as yet another 'fact on the ground' that Israel could defend on the grounds that retreat would only encourage the evil-doers. Well, the first invasion of Lebanon was even more ambitious in its aims. Israel believed that in alliance with the Phalangists, it could control up to two-thirds of Lebanese territory. Given Israel's long-standing obsession with the 'demographic problem', moreover, it would not be sensible for them to annexe the territory without being sure that they could control, deplete and expel the Palestinians in that territory.

As usual, Israel's aggression was prepared by various provocative actions designed to elicit a response from the PLO, including 'training exercises' in Lebanese territory, attacks on Lebanese fishing boats and violations of air and water space. No retort was forthcoming. So, following the attempted assassination of Israeli ambassador Shlomo Argov by the Abu Nidal group, Israel launched a series of bombing raids in Lebanese territory (where the Abu Nidal group did not have a presence). The PLO did respond this time, shelling northern colonies - or settlements, or villages, or 'Jewish residences', or whatever euphemism you prefer. Israel took the cue to invade, protestings its determination to crush terrorism and protect its civilians from shelling (does this sound vaguely familiar?). In reality it embarked on the attempted annihilation of the PLO as a physical force of resistance, and of the whole idea of independent Palestinian nationhood. And it is in this context that one must understand the Sabra and Shatila massacre.

The PLO was, Israel recognised, not merely a military or paramilitary outfit, but a popular political force well-rooted in the exiled Palestinian population. To attack the PLO was not just to attack their troops, but the whole civilian infrastructure which supported them. And it wasn't enough to attack them in Lebanon. It is forgotten, perhaps, that during the invasion Israel also quoshed a number of civic and elected institutions in the West Bank, imposing authoritarian rule by whatever proxies and quislings they could find (few in number as it happened). It set up, funded and armed Village Leagues to keep control of the territories, authorising them to carry out arrests and attacks on opponents. This is the role that, sadly, Fatah has come to embrace. In Lebanon, the annihilationist motif was evident from the beginning. Long before Sabra and Shatila, the earliest targets of the war included refugee camps such as Rashidiyeh, which was reduced to rubble. Its residents fled or were killed, and those who were caught were rounded up and taken to a nearby beach to watch the destruction. All males of teenage years and older were blindfolded, handcuffed, and taken away. And they were not heard from again. Again, the Ain el-Hilweh refugee camp was largely flattened by bombing, and its mosque bulldozed afterwards. Approximately 100 mangled bodies were found under the mosques ruins. Hospitals were destroyed, orphanages flattened by cluster and phosphorus bombs, a school in Sidon was destroyed with 300 inside killed and, with ruthless efficiency, the Israeli army blew housing blocks and apartments to craters, if they suspected that there might be PLO activists inside. Hundreds of thousands of refugees - mostly women and children, since males were more robustly dealt with - were wandering aimlessly through Lebanon's carnage, starving and out of their minds with terror, before Sabra and Shatila. And all the while, incidentally, liberal and left-wing figures from the United States were taking IDF tours of southern Lebanon, cheering on the bloodshed. Jane Fonda, who had funded the Viet Cong, found herself conscripted to Israel's army of overseas cheerleaders, as did Tom Hayden, the former Sixties radical. Michael Walzer's verdict can be summarised in the simple phrase: "just war".

In September 1982, a month after Israel's demolition of the PLO had been consecrated, the IDF sealed off the Sabra and Shatila refugee camp. On Thursday 16 September 1982, truckloads of Phalangist and Haddad troops entered the camp from behind IDF lines. The Phalangists selected for the attack were drawn from the most extreme elements of the militia, while the Haddad troops were more or less direct auxiliaries of the Israeli army. They killed and killed for days. At night, they killed by they light of flares, methodically massacring the inhabitants, scooping them up with bulldozers and burying them under the rubble. Those bodies which could not be buried were taken away in trucks. On Friday 17 September, the Israeli chief of staff and met with the Phalangist high command, commended their hard work, and offered them a truck with IDF markings so that they might better do their work. They were given another 12 hours in the camp to finish their work, which they duly completed by 5am on Saturday 18 September. After the massacre was completed, journalists began to arrive on the scene. Robert Fisk was one of them, and reported:

"What we found inside the Palestinian Chatila camp at ten o'clock on the morning of 18th September 1982 did not quite beggar description, although it would have been easier to re-tell in the cold prose of a medical examination ... there were women lying in houses with their skirts torn up to their waists and their legs wide apart, children with their throats cut, rows of young men shot in the back after being lined up at an execution wall. There were babies - blackened babies because they had been slaughtered more than 24 hours earlier and their small bodies were already in a state of decomposition - tossed into the rubbish heaps alongside discarded US army ration tins, Israeli army medical equipment and empty bottles of whisky ... Down a laneway to our right, no more than 50 yards from the entrance, there lay a pile of corpses. There were more than a dozen of them, young men whose arms and legs had been wrapped around each other in the agony of death. All had been shot at point-blank range through the cheek, the bullet tearing away a line of flesh up to the ear and entering the brain. Some had vivid crimson or black scars down the left side of their throats. One had been castrated, his trousers torn open and a settlement of flies throbbing over his torn intestines.

"The eyes of these young men were all open. The youngest was only 12 or 13 years old ... On the other side of the main road, up a track through the debris, we found the bodies of five women and several children. The women were middle-aged and their corpses lay draped over a pile of rubble. One lay on her back, her dress torn open and the head of a little girl emerging from behind her. The girl had short, dark curly hair, her eyes were staring at us and there was a frown on her face. She was dead ... One of the women also held a tiny baby to her body. The bullet that had passed through her breast had killed the baby too. Someone had slit open the woman's stomach, cutting sideways and then upwards, perhaps trying to kill her unborn child. Her eyes were wide open, her dark face frozen in horror." (Robert Fisk, Pity The Nation: Lebanon At War, Oxford University Press, 1992).

The UN General Assembly considered this an act of genocide. It is important to see this in light of the processes that led to the massacre. It was not an isolated incident, but the horrifying - from the IDF's perspective, apparently, glorious - culmination of Israel's war on the very idea of the Palestinian people. It has a genocidal logic which has been repeatedly expressed in the various massacres in Israel's wars, whether in Qana or in Gaza, where the IDF seemed to go out of its way to violate every last humanitarian norm - indeed, to prove that it absolutely did not consider the Palestinians worthy of even the most minimal human consideration. The incident in Gaza City, on 22 January this year, in which the IDF sealed off a neighbourhood, bombed and shelled it, blocked medical and humanitarian entry, and knowingly left children to slowly die next to their already deceased relatives, was a clear indication of this. Remembering Sabra and Shatila is not just about paying ritual tribute to the dead, for whom tributes are worthless. It is about knowing what it is that the Palestinians are up against, and understanding the urgent need for solidarity today. The TUC's support for the BDS campaign is long belated recognition of that.