This month marks the 10th anniversary of the first major military assault on the 2 million Palestinians of the Gaza Strip. After its unilateral withdrawal from Gaza in 2005, Israel turned the area into the biggest open-door prison on Earth. The two hallmarks of Israel’s treatment of Gaza since then have been mendacity and the utmost brutality towards civilians.

On 27 December 2008, Israel launched Operation Cast Lead, pounding the densely populated strip from the air, sea and land for 22 days. It was not a war or even “asymmetric warfare” but a one-sided massacre. Israel had 13 dead; the Gazans had 1,417 dead, including 313 children, and more than 5,500 wounded. According to one estimate 83% of the casualties were civilians. Israel claimed to be acting in self-defence, protecting its civilians against Hamas rocket attacks. The evidence, however, points to a deliberate and punitive war of aggression. Israel had a diplomatic alternative, but it chose to ignore it and to resort to brute military force.

In June 2008 Egypt had brokered a ceasefire between Israel and Hamas, the Islamic resistance movement that rules Gaza. The agreement called on both sides to cease hostilities and required Israel to gradually ease the illegal blockade it had imposed on the Gaza Strip in June 2007. This ceasefire worked remarkably well – until Israel violated it by a raid on 4 November in which six Hamas fighters were killed. The monthly average of rockets fired from Gaza on Israel fell from 179 in the first half of 2008 to three between June and October.

The story of the missed opportunity to avoid war was told to me by Robert Pastor, a professor of political science at the American University in Washington DC and a senior adviser on conflict resolution in the Middle East at the Carter Center NGO. Here is what Pastor told me over the phone and later confirmed in an email to Dr Mary Elizabeth King, another close associate of President Carter, on 8 December 2013, a month before Pastor’s death.

Pastor met Khaled Mashaal, the Hamas politburo chief, in Damascus in December 2008. Mashaal handed him a written proposal on how to restore the ceasefire. In effect, it was a proposal to renew the June 2008 ceasefire agreement on the original terms. Pastor then travelled to Tel Aviv and met Major General (Ret) Amos Gilad, head of the defence ministry’s political affairs bureau. Gilad promised that he would communicate the proposal directly to defence minister Ehud Barak, and expected to have an answer either that evening or the following day. The next day, Pastor phoned Gilad’s office three times and got no response. Shortly afterwards, Israel launched Operation Cast Lead.

‘Emblematic of everything that is wrong with Israel’s approach to Gaza.’ An Israeli strike near a UN school in Beit Lahia, January 2009. Photograph: Mohammed Abed/AFP/Getty Images

In the email he dictated to his son on his deathbed, Pastor authorised me to publicise this story and to attribute it to him because “it’s an important moment in history that Israel needs to accept because Israel had an alternative to war in December 2008”. It was indeed a critical moment and it conveyed a clear message: if Israel’s real purpose was to protect its civilians, all it needed to do was to follow Hamas’s example by observing the ceasefire.

Israel’s conduct during the first Gaza war was placed under an uncompromising lens by the UN Human Rights Council’s independent fact-finding mission headed by Richard Goldstone, the distinguished South African judge who happened to be both a Jew and a Zionist. Goldstone and his team found that both Hamas and the Israel Defence Forces had committed violations of the laws of war by deliberately harming civilians. The IDF received more severe strictures than Hamas on account of the bigger scale and seriousness of its violations.

The Goldstone team investigated 36 incidents involving the IDF. It found 11 incidents in which Israeli soldiers launched direct attacks against civilians with lethal outcomes; seven where civilians were shot leaving their homes waving white flags; a “direct and intentional” attack on a hospital; numerous incidents where ambulances were prevented from attending to the severely injured; and nine attacks on civilian infrastructure with no military significance, such as flour mills, sewage works, and water wells – all part of a campaign to deprive civilians of basic necessities. In the words of the report, much of this extensive damage was “not justified by military necessity and carried out unlawfully and wantonly”.

In conclusion, the 575-page report noted that while the Israeli government sought to portray its operations as essentially a response to rocket attacks in the exercise of the right to self-defence, “the Mission itself considers the plan to have been directed, at least in part, at a different target: the people of Gaza as a whole”. Under the circumstances “the Mission concludes that what occurred in just over three weeks at the end of 2008 and the beginning of 2009 was a deliberately disproportionate attack designed to punish, humiliate and terrorise a civilian population, radically diminish its local economic capacity both to work and to provide for itself, and to force upon it an ever-increasing sense of dependency and vulnerability.”

The claim that the operation was designed to “terrorise a civilian population” needs underlining. Terrorism is the use of force against civilians for political purposes. By this definition Operation Cast Lead was an act of state terrorism. The political aim was to force the population to repudiate Hamas, which had won a clear majority in the elections of January 2006.

Operation Cast Lead is emblematic of everything that is wrong with Israel’s approach to Gaza. The Israeli-Palestinian conflict is a political conflict to which there is no military solution. Yet Israel persists in shunning diplomacy and relying on brute military force – and not as a last resort but as a first resort. Force is the default setting. And there is a popular Israeli saying that goes with it: “If force doesn’t work, use more force!”

Operation Cast Lead was just the first in a series of Israeli mini-wars on Gaza. It was followed by Operation Pillar of Defence in November 2012 and Operation Protective Edge in the summer of 2014. The fancy names given to these operations were fraudulent, dressing up offensive attacks on defenceless civilians and civilian infrastructure in the sanctimonious language of self-defence. They are typical examples of Orwellian double-speak. UN secretary general Ban Ki-moon called the Israeli attack on 1 August 2014 on Rafah, in which a large number of civilians sheltering in UN schools were killed, “a moral outrage and a criminal act”. This description applies equally to Israel’s entire policy of waging war on the inmates of the Gaza prison.

Israeli generals talk about their recurrent military incursions into Gaza as “mowing the lawn”. This operative metaphor implies a task that has to be performed regularly and mechanically and without end. It also alludes to the indiscriminate slaughter of civilians and the inflicting of damage on civilian infrastructure that takes several years to repair.

“Mowing the lawn” is a chilling euphemism but it provides a clue as to the deeper purpose behind Israel’s steadfast shunning of diplomacy and repeated resort to brute military force in response to all manifestations of lawful resistance and peaceful protest on its southern border. Under this grim rubric, there can be no lasting political solution: the next war is always just a matter of time.

• This article was amended on 8 January 2019 to correct the date in Robert Pastor’s email from his death bed from 2018 to 2008

• Avi Shlaim is an emeritus professor of international relations at Oxford and the author of The Iron Wall: Israel and the Arab World