Before you rush to judgement on the iniquity of Israel's lethal air strikes on the Gaza Strip – your own judgement, not a judgement borrowed from flailing politicians or vocal lobbyists for either side – could you answer one question.

Have you ever been to Israel? I don't mean have you looked at a map of the Middle East or glanced across from the beach in Aqaba, or even visited the slums that, more than 50 years on, are absurdly still called Palestinian refugee camps. I mean have you ever been to Israel?

Because if you have, you might understand how small and devoid of natural defences this country is. You would see that from north, south and east, they are vulnerable to siege from those who command the higher ground and the escape routes. And you would realise how fearful Israelis remain, even three generations on, that they could actually be driven into the sea in a matter of hours.

And a second question, if I may. Deep down, do you believe that the state of Israel has a right to exist, or do you feel, if you are brutally honest, that the world would be a simpler and more harmonious place if only the victorious Second World War Allies had found a way of purging their post-Holocaust guilt without acquiescing in the creation of a Jewish homeland in what had been Palestine under the British mandate. Do you feel, even today, that Israel – and I'm talking about Israel, not the occupied territories – is Arab land that belongs, by ancestral right, to the Palestinians?

Well, I have been to Israel; I have driven the length and breadth of it in more peaceful times; I have talked to its leaders and people. My overwhelming impression is not of war-lust, but of insecurity. You might scorn as paranoia the concerns of a developed country that this year spent 16 per cent of its state budget on defence, counts the US as its protector, and – it is widely accepted – has developed a nuclear weapon. But you have a duty to ask what came first: the fear of annihilation or the military capability to pre-empt it.

As for Israel's right to exist, I do question the wisdom, let alone the justice, of planting a new state on land which someone else claims as historically theirs – Kosovo being a recent example. A country established artificially, with no regard to natural defences nor liberated by its own force, is liable to be not just vulnerable, but a source of friction for as long as the folk memory persists.

Such ingrained disapproval may well underlie the tendency in much of the Western world to blame Israel, almost before it has done anything at all. If only, runs the unspoken thought, Israel had not existed, or at least had not occupied this particular piece of ground, all this murderous conflict could have been avoided.

Both with Israel's fiercely condemned invasion of Lebanon two summers ago, and now with its air attacks on Gaza, however, these same two factors need to be kept in mind: on the one hand, Israel's continuing sense of its own insecurity; on the other, its internationally recognised right to exist. The point is that, having endorsed the creation of the state of Israel, the UN, as heir to the League of Nations, has an obligation to make sure that its continued existence is possible. Time and again, though, all manner of international guarantees have proved inadequate. Israel soon learnt that it would have to be able to look after itself.

It is a paradox that one of the most vulnerable states in the Middle East has thus gained the reputation of an aggressor and bully. Nor have its enemies been above exploiting aspects of that vulnerability. The Yom Kippur war of 1973 was so called because it was launched by Egypt and Syria on one of Judaism's holiest days. All the peace treaties that Israel has so far been able to negotiate with its neighbours have been achieved, as an Israeli might see it, from a position of military strength.

Israel's withdrawal from the Gaza Strip in the summer of 2005 was a rare instance of Israeli risk-taking – the first stage of a programme of withdrawals from occupied territory initiated, at some political peril, by the then Prime Minister, Ariel Sharon. It was a programme for which Mr Sharon received scant credit, either at the time he announced it or subsequently, because of a widespread assumption outside Israel that the military would manufacture some excuse not to comply.

Israel's gamble was that, left in charge, the Palestinian Authority would be able to prevent rocket – or any other sort of attacks – on Israel. In the event, the gamble was lost. The Palestinian Authority, despite its best efforts, was unable to keep its extremists in check. An election was held that was legitimately won by the fundamentalist organisation, Hamas. Prevented from taking, or even sharing, power in the overall Palestinian Authority, Hamas seized power in Gaza. Sporadic rocket-fire into Israel escalated. Earlier this month Hamas said it would not renew a six-month ceasefire. After new rocket-strikes, Israel – in the throes of a keenly fought election campaign – released its firepower. Once again, the Palestinians of Gaza have worn their victimhood as a badge of honour.

It might reasonably be asked how things might have been different. If the US and Israel had recognised the Hamas election victory; if the power-sharing deal between Fatah and Hamas had stuck; if Israel had not closed crossing-points with Gaza, citing its own security fears ... But this is not what happened.

Now, as with the Lebanon war, Israel's critics charge that its action in Gaza has been "disproportionate" – "proportionate", presumably, being a few home-made rockets fired into civilian areas of Gaza as and when. Israel might retort, not unreasonably, that if Hamas wants war, it can have it: Israel's fight is for its future security. What these same Western critics should be asking, however, is why Israel feels so threatened that it resorts to such force, knowing full well the international opprobrium that will follow.

And the answer is that if, in the past, the outside world – in the shape of the UN, the US, the Quartet or whoever – had shown itself willing and able to ensure Israel's security, then neither Israel nor the Gaza Palestinians need have resorted to force this winter. The excesses in Gaza, as in Lebanon before, are the consequence of a much earlier failure: the failure to enforce international law and truly guarantee Israel's right to exist.