So Dick Cheney was right. In the end, the Iraqi people did respond to American soldiers with flowers. The only trouble was, it was their shipping out, not their digging in, that the Iraqi people celebrated. On Tuesday, as US forces marked their formal withdrawal from the towns and cities they invaded more than six years ago, the Iraqi people showed the kind of spontaneous joy the former Vice-President once imagined would welcome the 173rd Airborne Brigade. There were streamers and balloons, pop concerts in the park and, yes, flowers — garlanding the abandoned checkpoints of the US military in petals.

Now, as Iraq recedes, it is the country next door that looms ever larger. Handled the wrong way, Iran threatens to define Barack Obama the way Iraq defined George W Bush.

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Is that a sign of things to come? Put simply, have the events of the last three weeks in Tehran made the prospect of US-led action against Iran — up to and including the use of military force — more or less likely? At first glance, those advocating regime change seem to have had a boost. The world has just watched a three-week infomercial exposing the brutality of Iran’s leaders. If it’s not allegations of a stolen election, including the black comedy of Monday’s announcement from the Guardian Council that, yes, there had been an error in the count and therefore Mahmoud Ahmadinejad’s vote would be revised upward — it’s the violence that has followed.

One western diplomat says opinion in the chancelleries of Europe has hardened, even among those once well-disposed towards Tehran: “They have seen the face of this regime — and it’s not pretty.”

What’s more, those eager for confrontation might find an all too willing partner in Iran’s rulers. Professor Ali Ansari, a noted authority on the country, predicts that a regime that now “suffers from a serious domestic legitimacy problem — and which knows it — will seek a foreign foe, something to rally the country around.” He predicts “acts of provocation,” and only hopes Israel is wise enough not to take the bait.

Above all, those pushing for regime change could find international public opinion more receptive than it would have been a month ago. Three weeks of YouTube footage, including the blood-spattered image of Neda Soltan, the female protester shot dead in cold blood, has surely created a well of public sympathy from which any advocate of action against the mullahs could draw. One can imagine the arguments as, in 2011, President Obama, backed by his loyal ally Prime Minister David Cameron of Britain, addresses the United Nations demanding a united show of strength to save the benighted people of Iran.

But the events of the last few weeks could point in the opposite direction too. Officially the US and UK