The scale of Israel's attack on the Gaza Strip, and the almost daily reports of war crimes over the last three weeks, has drawn criticism from even longstanding friends and sympathisers. Despite the Israeli government's long-planned and comprehensive PR campaign, hundreds of dead children is a hard sell. As a former Israeli government press adviser put it, in a wonderful bit of unintentional irony, "When you have a Palestinian kid facing an Israeli tank, how do you explain that the tank is actually David and the kid is Goliath?"

Despite a mass of evidence that includes Israel's targets in Operation Cast Lead, public remarks by Israeli leaders over some time, and the ceasefire manoeuvring of this last weekend, much of the analysis offered by politicians or commentators has been disappointingly limited, and characterised by false assumptions, or misplaced emphases, about Israel's motivations.

First, to what this war on Gaza is not about: it's not about the rockets. During the truce last year, rocket fire from the Gaza Strip was reduced by 97%, with the few projectiles that were fired coming from non-Hamas groups opposed to the agreement. Despite this success in vastly improving the security of Israelis in the south, Israel did everything it could to undermine the calm, and provoke Hamas into a conflict.

Israel broke the ceasefire on 4 November, with an attack in the Gaza Strip that killed six Hamas members, and the following day severely tightened its siege of the territory. Imports were reduced to 16 trucks a day, down from 123 daily just the previous month (and 475 in May 2007). Following the unsurprising surge in Palestinian attacks, Israeli officials claimed that an all-out war was unavoidable; without mentioning that an operation had been planned for some months already.

Second, the current operation is only in a limited sense related to both the upcoming Israeli elections and restoring the IDF's so-called deterrence. While it has been pointed out that a hardline approach to Palestinian "terrorism" can play well with the Israeli public, wars are not necessarily Israeli politicians' tactic of choice - the Lebanon war was fought a few months after one.

Israel is also supposed to be restoring the reputation and "deterrence factor" of its armed forces, after their humiliation in Lebanon in 2006. Suffice to say that until this weekend's unilateral ceasefire, in an aid-dependent enclave defended by an almost entirely isolated militia, Israel's operation had already lasted three times longer than the 1967 war when Israel defeated its Arab neighbours and occupied the rest of Mandate Palestine.

These three suggested motivations have sometimes reached the level of assumed knowledge, providing the background for further comment and reporting. Based on this kind of analysis, then, criticism of Palestinian civilian casualties is framed as "disproportionate" or "heavy-handed", but fundamentally a case of self-defence. It is understood that any democratic nation would have to respond to terrorist rocket fire, but Israel has gone a bit too far.

There is, however, no shortage of evidence available that points to rather different Israeli aims. Estimates for the proportion of civilian deaths among the 1,360 Palestinians killed range from more than half to two-thirds. Politicians, diplomats and journalists are by and large shying away from the obvious, namely that Israel has been deliberately targeting Palestinian civilians and the very infrastructure of normal life, in order to - in the best colonial style - teach the natives a lesson.

Given the enormous scale of what Palestinians have described as a "war of extermination" - it appears that some 15% of all buildings in the Gaza Strip were completely destroyed or collapsed and there is an estimated $1.4bn worth of destruction to vital civil infrastructure - it is impossible to list every atrocity. Israel has repeatedly hit ambulances, medics, clinics, and hospitals, while last week, aid volunteers who tried to douse a fire in a Red Crescent warehouse (attacked by Israel) were then shot at by Israeli forces.

UNRWA facilities have also been attacked, including several schools sheltering civilians - just this last weekend, a civilian refuge was repeatedly shelled. Last week, the UN headquarters was also shelled, hitting a vocational centre, a workshop, food warehouse, and fuel depot. Like the massacre of 6 January, Israeli officials quickly began to produce a confusing fog of denials, apologies, promised enquiries and contradictions.

Those are just some of the more shocking examples from a military operation that has targeted everything from schools, money-changers and a bird farm, to entire apartment blocks, harbours, and a market. Palestinians have been killed when Israeli tanks fired shells at residential neighbourhoods. Every day has brought fresh horrors; last Wednesday, for example, 70 unarmed civilians including 18 children were killed by the Israeli military. This week's Observer carried a story alleging Israel bulldozed homes with civilians inside (not for the first time) and shot those waving white flags. Little wonder that Israeli officials predicted with concern that "negative sentiment" towards the state would "only grow as the full picture of destruction emerges".

Much of this is widely known, and easily accessible; yet still the analytical emphasis has remained on Palestinian rockets, Israeli elections, and deterrence. I would like to suggest three alternative purposes for Israel's Operation Cast Lead that go beyond the usual perspectives, and presuming with Yale professor David Bromwich that "if Israel in 2009 reduces to rubble a large portion of the Gaza Strip and leaves tens of thousands homeless, there is a strong chance that this was what it intended to do".

The first aim is to humiliate and weaken Hamas. On the one hand, this seems obvious, but contrary to how the goal is often understood, this is not primarily to protect the Israeli public - as pointed out previously, ceasefires and negotiations are far more likely to deliver security for Israeli citizens - but rather it is a political goal. Hamas had withstood isolation, a siege, mass arrests, and an attempted western-backed coup. Moreover, cracks were appearing in the international community's resolve to parrot Israel's line on Hamas. The group, with its resilience and ability to deliver on negotiated ceasefires, was threatening the chance to make a deal with the Ramallah "moderates", and so:

A hammer blow that shattered the movement, launching some of the resulting splinters in directions that once again put all of them beyond the pale, was the most effective way to keep at bay those third parties reaching the conclusion that engaging rather than excluding Hamas could enhance the prospects of peace.

Back in December, before both the end of the six-month truce and the start of Operation Cast Lead, foreign minister Tzipi Livni stated that an extended truce "harms the Israel strategic goal, empowers Hamas, and gives the impression that Israel recognizes the movement". By the end of the month, Livni would be telling a press conference that "Hamas wants to gain legitimacy from the international community" and stressing that it is "important to keep Hamas from becoming a legitimate organisation" (apparently winning a democratic election isn't enough to confer legitimacy).

Just as Israel chose "blood over diplomacy" in order to avoid enhancing "Hamas's image as a responsible interlocutor", so this weekend, Israel chose a unilateral ceasefire for the same reason, "hoping to send the message that Hamas is not a legitimate actor". A war begun in order to delegitimise Hamas would not make way for a ceasefire in which Hamas was a partner at the negotiating table.

Hence Israel decided to shortcut the Egyptian-driven efforts at securing a ceasefire, and opt for a unilateral approach that allows Israel, the US, Egypt, Mahmoud Abbas, Britain - in fact, every interested party, except the Gaza Strip authorities - to work together on an apparent solution. It is also worth pointing out that the unilateral nature of the ceasefire frees Israel to define an infringement or collapse on its own terms.

The second aim of Israel's war is to teach a lesson to the Palestinians in Gaza, and elsewhere, that the only way to avoid the wrath of the Israeli military is to accept Israel's idea of a two-state solution, a generous concession to be gratefully received by Abbas and fellow moderates. It is a reflection of the approach outlined by the IDF chief of staff, Moshe Ya'alon, in 2002 that "the Palestinians must be made to understand in the deepest recesses of their consciousness that they are a defeated people".

On 4 January, Israeli President Shimon Peres said that Hamas needed "a real and serious lesson"; days later, he was more explicit, reportedly declaring Israel's aim to be "to provide a strong blow to the people of Gaza so that they would lose their appetite for shooting at Israel". The next day, the Washington Post also described how Israeli officials were hoping that the attacks would mean "that Gazans become disgusted with Hamas and drive the group from power".

This Israeli strategy was previously deployed in Lebanon in 2006, when senior military commanders redefined civilian villages as "military bases" which would be subjected to "disproportionate force" causing "great damage and destruction". As I previously noted, the lessons learned in Lebanon were not just wrong, but criminal: a retired IDF major general and former adviser to the prime minister, Giora Eiland, reflected in a paper that "the destruction of homes and infrastructure and the suffering of hundreds of thousands of people are consequences that can influence Hezbollah's behaviour more than anything else".

Ironically, the same Peres who now justifies collective punishment, in 2002 chastised Avigdor Lieberman for suggesting that the IDF should bomb civilian targets, warning the minister that such a tactic would be a war crime. The last three weeks show that proposals made by Israel's political extremists and originally considered outlandish, do not take long to become normal policy.

Deliberately targeting civilians and vital infrastructure for political purposes links smoothly, into the post-conflict phase, with the Israeli and US plan to try and rescue the deeply discredited image of the Palestinian Authority through a politicised reconstruction of the Gaza Strip. As US state department spokesman Sean McCormack coyly put it, the "military solution" must be followed up by investing in infrastructure and helping the population "so that they can make a different kind of political decision".

The third aim of Israel's attack on the Gaza Strip is to further "catastrophise" the territory, reducing the capacity for continued existence to the barest of minimums - perhaps to bring about "an end to the persistence of Gaza's ordinary people in wanting the chance of a peaceful and dignified life". One obvious benefit to Israel of pulverising "civilian Palestinian infrastructure" is that "people who lack collective institutions and are reduced to scrabbling for their very survival are easier to dominate".

Yet, there is more going on here. Israel seeks to turn the Gaza Strip into a depoliticised humanitarian crisis, always on the brink of catastrophe, always dependent; its population reduced to ration-receiving clients of international aid. Yitzhak Rabin famously wished that Gaza "would just sink into the sea", but perhaps the best Israel can do is to share the problem with the international community, possibly to the extent of troops on the ground.

Increasingly focusing on Egyptian responsibility is also part of this, whether in terms of arms smuggling, aid supplies, or for some, direct rule.

In all of this, the Gaza Strip has become a laboratory for future possible scenarios in the West Bank (where a process of "development-isation" and NGO-funded occupation is well established). All three of these Israeli aims - to delegitimise and sideline Hamas, to persuade Palestinians to give up their resistance and to shirk responsibility for a shattered Gaza Strip - require the deliberate commission of war crimes and gross human rights abuses. As time will tell, they are also doomed to fail.