The way western politicians and media have pontificated about Israel's onslaught on Gaza, you'd think it was facing an unprovoked attack from a well-armed foreign power. Israel had every "right to defend itself", Barack Obama declared. "No country on earth would tolerate missiles raining down on its citizens from outside its borders."

He was echoed by Britain's foreign secretary, William Hague, who declared that the Palestinian Islamists of Hamas bore "principal responsibility" for Israel's bombardment of the open-air prison that is the Gaza Strip. Meanwhile, most western media have echoed Israel's claim that its assault is in retaliation for Hamas rocket attacks; the BBC speaks wearisomely of a conflict of "ancient hatreds".

In fact, an examination of the sequence of events over the last month shows that Israel played the decisive role in the military escalation: from its attack on a Khartoum arms factory reportedly supplying arms to Hamas and the killing of 15 Palestinian fighters in late October, to the shooting of a mentally disabled Palestinian in early November, the killing of a 13 year-old in an Israeli incursion and, crucially, the assassination of the Hamas commander Ahmed Jabari last Wednesday during negotiations over a temporary truce.

Israel's prime minister, Binyamin Netanyahu, had plenty of motivation to unleash a new round of bloodletting. There was the imminence of Israeli elections (military attacks on the Palestinians are par for the course before Israeli polls); the need to test Egypt's new Muslim Brotherhood president, Mohamed Morsi, and pressure Hamas to bring other Palestinian guerrilla groups to heel; and the chance to destroy missile caches before any confrontation with Iran, and test Israel's new Iron Dome anti-missile system.

So after six days of sustained assault by the world's fourth largest military power on one of its most wretched and overcrowded territories, at least 130 Palestinians had been killed, an estimated half of them civilians, along with five Israelis. The goal, Israel's interior minister, Eli Yeshai, insisted, had been to "send Gaza back to the middle ages".

True, the bloodshed hasn't so far been on the scale of Operation Cast Lead in 2008-9, which left 1,400 Palestinians dead in three weeks. But the issue isn't just who started and escalated it, or even the grinding "disproportionality" of yet another Israeli military battering (even before last month's flareups, 314 Palestinians had been killed since 2009, as against 20 Israelis).

It's that to portray Israel as some kind of victim with every right to "defend itself" from attack from "outside its borders" is a grotesque inversion of reality. Israel has after all been in illegal occupation of both the West Bank and Gaza, where most of the population are the families of refugees who were driven out of what is now Israel in 1948, for the past 45 years.

Despite Israel's withdrawal of settlements and bases in 2005, the Gaza Strip remains occupied, both effectively and legally – and is recognised as such by the UN. Israel is in control of Gaza's land and sea borders, territorial waters and natural resources, airspace, power supply and telecommunications. It has blockaded the strip since Hamas took over in 2006-7, preventing the movement of people, materials, and food supplies in and out of the territory – even calculating the 2,279 calories per person that would keep Gazans on an exemplary "diet". And it continues to invade the strip at will.

So Gazans are an occupied people and have the right to resist, including by armed force (though not to target civilians), while Israel is an occupying power that has an obligation to withdraw – not a right to defend territories it controls or is colonising by dint of military power.

Even if Israel had genuinely ended its occupation in 2005, Gaza's people are Palestinians, and their territory part of the 22% of historic Palestine earmarked for a Palestinian state that depends on Israeli withdrawal from the occupied West Bank and east Jerusalem. Across their land, Palestinians have the right to defend and arm themselves, whether they choose to exercise it or not.

But instead the US, Britain and other European powers finance, arm and back to the hilt Israel's occupation, including the siege of Gaza – precisely to prevent Palestinians obtaining the arms that would allow them to protect themselves against Israeli military might.

It's hardly surprising of course that powers which have themselves invaded, occupied and intervened across the Arab and Muslim world over the last decade should throw their weight behind Israel doing the same thing on its own doorstep. But it isn't Palestinian rockets that stop Israel lifting the blockade, dismantling its illegal settlements or withdrawing from the West Bank and Gaza – it's unconditional US and western support that gives Israel impunity.

Whatever the Israeli government's mix of motivations for winding up the past week's conflict, it seems to have backfired. For the first time since the start of the Arab uprisings, the cause of Palestine is again centre stage.

Emboldened by the wave of change and growing support across the region, Hamas has also regained credibility as a resistance force, which had faded since 2009, and strengthened its hand against an increasingly discredited Palestinian Authority leadership in Ramallah. The deployment of longer-range rockets that have now been shown to reach Tel Aviv and Jerusalem is also beginning to shift what has been an overwhelmingly one-sided balance of deterrence.

The truce being negotiated on Tuesday would reportedly enforce Hamas responsibility for policing the strip and crucially break the blockade, opening the Rafah crossing with Egypt for goods as well as people. It doesn't, however, look like the long-term security deal with Hamas Israel was looking for, which would risk deepening the disastrous Palestinian split between Gaza and the West Bank.

Any relief from the bombardment, death and suffering of the past week has got to be welcome. But no ceasefire is going to prevent another eruption of violence. Whatever is finally agreed won't end Israel's occupation and colonisation of Palestinian land or halt its war of dispossession against the Palestinian people. That demands unrelenting pressure on the western powers that underwrite it to change course. But most of all, it needs a change in the balance of forces on the ground.

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