Whatever we think of Israel's assault on Lebanon, all of us seem to agree about one fact: that it was a response, however disproportionate, to an unprovoked attack by Hizbullah. I repeated this "fact" in my last column, when I wrote that "Hizbullah fired the first shots". This being so, the Israeli government's supporters ask peaceniks like me, what would you have done? It's an important question. But its premise, I have now discovered, is flawed.

Since Israel's withdrawal from southern Lebanon in May 2000, there have been hundreds of violations of the "blue line" between the two countries. The United Nations Interim Force in Lebanon (Unifil) reports that Israeli aircraft crossed the line "on an almost daily basis" between 2001 and 2003, and "persistently" until 2006. These incursions "caused great concern to the civilian population, particularly low-altitude flights that break the sound barrier over populated areas". On some occasions, Hizbullah tried to shoot them down with anti-aircraft guns.

In October 2000, the Israel Defence Forces shot at unarmed Palestinian demonstrators on the border, killing three and wounding 20. In response, Hizbullah crossed the line and kidnapped three Israeli soldiers. On several occasions, Hizbullah fired missiles and mortar rounds at IDF positions, and the IDF responded with heavy artillery and sometimes aerial bombardment. Incidents like this killed three Israelis and three Lebanese in 2003; one Israeli soldier and two Hizbullah fighters in 2005; and two Lebanese people and three Israeli soldiers in February 2006. Rockets were fired from Lebanon into Israel several times in 2004, 2005 and 2006, on some occasions by Hizbullah. But, the UN records, "none of the incidents resulted in a military escalation".

On May 26 this year, two officials of Islamic Jihad - Nidal and Mahmoud Majzoub - were killed by a car bomb in the Lebanese city of Sidon. This was widely assumed in Lebanon and Israel to be the work of Mossad, the Israeli intelligence agency. In June, a man named Mahmoud Rafeh confessed to the killings and admitted that he had been working for Mossad since 1994. Militants in southern Lebanon responded, on the day of the bombing, by launching eight rockets into Israel. One soldier was lightly wounded. There was a major bust-up on the border, during which one member of Hizbullah was killed and several wounded, and one Israeli soldier wounded. But while the border region "remained tense and volatile", Unifil says it was "generally quiet" until July 12.

There has been a heated debate on the internet about whether the two Israeli soldiers kidnapped by Hizbullah that day were captured in Israel or in Lebanon, but it now seems pretty clear that they were seized in Israel. This is what the UN says, and even Hizbullah seems to have forgotten that they were supposed to have been found sneaking around the outskirts of the Lebanese village of Aita al-Shaab. Now it simply states that "the Islamic resistance captured two Israeli soldiers at the border with occupied Palestine". Three other Israeli soldiers were killed by the militants. There is also some dispute about when, on July 12, Hizbullah first fired its rockets; but Unifil makes it clear that the firing took place at the same time as the raid - 9am. Its purpose seems to have been to create a diversion. No one was hit.

But there is no serious debate about why the two soldiers were captured: Hizbullah was seeking to exchange them for the 15 prisoners of war taken by the Israelis during the occupation of Lebanon and (in breach of article 118 of the third Geneva convention) never released. It seems clear that if Israel had handed over the prisoners, it would - without the spillage of any more blood - have retrieved its men and reduced the likelihood of further kidnappings. But the Israeli government refused to negotiate. Instead - well, we all know what happened instead. Almost 1,000 Lebanese and 33 Israeli civilians have been killed so far, and a million Lebanese displaced from their homes.

On July 12, in other words, Hizbullah fired the first shots. But that act of aggression was simply one instance in a long sequence of small incursions and attacks over the past six years by both sides. So why was the Israeli response so different from all that preceded it? The answer is that it was not a reaction to the events of that day. The assault had been planned for months.

The San Francisco Chronicle reports that "more than a year ago, a senior Israeli army officer began giving PowerPoint presentations, on an off-the-record basis, to US and other diplomats, journalists and thinktanks, setting out the plan for the current operation in revealing detail". The attack, he said, would last for three weeks. It would begin with bombing and culminate in a ground invasion. Gerald Steinberg, professor of political science at Bar-Ilan University, told the paper that "of all of Israel's wars since 1948, this was the one for which Israel was most prepared ... By 2004, the military campaign scheduled to last about three weeks that we're seeing now had already been blocked out and, in the last year or two, it's been simulated and rehearsed across the board".

A "senior Israeli official" told the Washington Post that the raid by Hizbullah provided Israel with a "unique moment" for wiping out the organisation. The New Statesman's editor, John Kampfner, says he was told by more than one official source that the US government knew in advance of Israel's intention to take military action in Lebanon. The Bush administration told the British government.

Israel's assault, then, was premeditated: it was simply waiting for an appropriate excuse. It was also unnecessary. It is true that Hizbullah had been building up munitions close to the border, as its current rocket attacks show. But so had Israel. Just as Israel could assert that it was seeking to deter incursions by Hizbullah, Hizbullah could claim - also with justification - that it was trying to deter incursions by Israel. The Lebanese army is certainly incapable of doing so. Yes, Hizbullah should have been pulled back from the Israeli border by the Lebanese government and disarmed. Yes, the raid and the rocket attack on July 12 were unjustified, stupid and provocative, like just about everything that has taken place around the border for the past six years. But the suggestion that Hizbullah could launch an invasion of Israel or that it constitutes an existential threat to the state is preposterous. Since the occupation ended, all its acts of war have been minor ones, and nearly all of them reactive.

So it is not hard to answer the question of what we would have done. First, stop recruiting enemies, by withdrawing from the occupied territories in Palestine and Syria. Second, stop provoking the armed groups in Lebanon with violations of the blue line - in particular the persistent flights across the border. Third, release the prisoners of war who remain unlawfully incarcerated in Israel. Fourth, continue to defend the border, while maintaining the diplomatic pressure on Lebanon to disarm Hizbullah (as anyone can see, this would be much more feasible if the occupations were to end). Here then is my challenge to the supporters of the Israeli government: do you dare to contend that this programme would have caused more death and destruction than the current adventure has done?

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