When you invade someone else's country, there has to be a first soldier, just as there has to be a last. The first man in front of the first unit of the first column of the invading American army to reach Fardous Square in the centre of Baghdad in 2003 was Corporal David Breeze of the 3rd Battalion, Fourth Marine Regiment. For that reason, of course, he pointed out to me that he wasn't a soldier at all. Marines are not soldiers. They are Marines. But he hadn't talked to his mom for two months and so – equally inevitably – I offered him my satellite phone to call his home in Michigan. Every journalist knows you'll get a good story if you lend your phone to a soldier in a war.

"Hi, you guys," Breeze bellowed. "I'm in Baghdad. I'm ringing to say 'Hi! I love you. I'm doing fine. I love you guys.' The war will be over in a few days. I'll see you soon."

Yes, they all said the war would be over soon. They didn't consult the Iraqis about this pleasant notion. The first suicide bombers – a policeman in a car and then two women in a car – had already hit the Americans on the long highway up to Baghdad. There would be hundreds more. There will be hundreds more in Iraq in the future.

So we should not be taken in by the tomfoolery on the Kuwaiti border in the past few days, the departure of the last "combat" troops from Iraq two weeks ahead of schedule. Nor by the infantile cries of "We won" from teenage soldiers, some of whom must have been 12 years old when George W Bush sent his army off on this catastrophic Iraqi adventure. They are leaving behind 50,000 men and women – a third of the entire US occupation force – who will be attacked and who will still have to fight against the insurgency.

Yes, officially they are there to train the gunmen and militiamen and the poorest of the poor who have joined the new Iraqi army, whose own commander does not believe they will be ready to defend their country until 2020. But they will still be in occupation – for surely one of the "American interests" they must defend is their own presence – along with the thousands of armed and undisciplined mercenaries, western and eastern, who are shooting their way around Iraq to safeguard our precious western diplomats and businessmen. So say it out loud: we are not leaving.

Instead, the millions of American soldiers who have passed through Iraq have brought the Iraqis a plague. From Afghanistan – in which they showed as much interest after 2001 as they will show when they start "leaving" that country next year – they brought the infection of al-Qaeda. They brought the disease of civil war. They injected Iraq with corruption on a grand scale. They stamped the seal of torture on Abu Ghraib – a worthy successor to the same prison under Saddam's vile rule – after stamping the seal of torture on Bagram and the black prisons of Afghanistan. They sectarianised a country that, for all its Saddamite brutality and corruption, had hitherto held its Sunnis and Shias together.

And because the Shias would invariably rule in this new "democracy", the American soldiers gave Iran the victory it had sought so vainly in the terrible 1980-88 war against Saddam. Indeed, men who had attacked the US embassy in Kuwait in the bad old days – men who were allies of the suicide bombers who blew up the Marine base in Beirut in 1983 – now help to run Iraq. The Dawa were "terrorists" in those days. Now they are "democrats". Funny how we've forgotten the 241 US servicemen who died in the Lebanon adventure. Corporal David Breeze was probably two or three years old then.

But the sickness continued. America's disaster in Iraq infected Jordan with al-Qaeda – the hotel bombings in Amman – and then Lebanon again. The arrival of the gunmen from Fatah al-Islam in the Nahr al-Bared Palestinian camp in the north of Lebanon – their 34-day war with the Lebanese army – and the scores of civilian dead were a direct result of the Sunni uprising in Iraq. Al-Qaeda had arrived in Lebanon. Then Iraq under the Americans re-infected Afghanistan with the suicide bomber, the self-immolator who turned America's soldiers from men who fight to men who hide.

Anyway, they are busy rewriting the narrative now. Up to a million Iraqis are dead. Tony Blair cares nothing about them: they do not feature, please note, in his royalties generosity. And nor do most of the American soldiers. They came. They saw. They lost. And now they say they've won. How the Arabs must be hoping for no more victories like this one.

Iraq by numbers

3,000 The estimated number of Iraqi civilians killed last year. That's less than a tenth of the 34,500 killed in 2007 but it's still testament to the dangers faced each day by Iraqis.

200 The number of Iraqis known to be still held in US custody – a fraction of the 26,000 held in military prisons three years ago.

15.5 The average number of hours of electricity a day Baghdad receives, a marked improvement on the six hours it got three years ago but still not up to pre-invasion standards, when Iraqi cities could rely on 24-hour power.