Try doing that now and you can order your body bag in advance. Every humvee has a sign fixed to its back warning that any attempts to approach closer than 100 yards will mean the gunner on the roof will open fire. Civilian cars scatter before US patrols like jittery deer before a wolf.

The reason for such nervousness is the American military death toll, which after the death of a US Marine in Ramadi yesterday, stood three short of 2,000. In the chaotic days that followed the fall of Saddam Hussein in 2003, and with President Bush declaring mission accomplished, the death of any US soldier was a news story. Journalists would grab their flak jackets, jump in their cars and speed off to Fallujah or Boura in southern Baghdad; mobs of angry Iraqis would be milling around a smouldering humvee or pool of blood, shouting their anger at the lack of electricity, or water or security.

In the early days the attacks had an almost casual air: a teenager would drop a hand grenade off a bridge into a passing humvee; a lone attacker would emerge with a rocket-propelled grenade launcher and fire at soldiers buying air-conditioning units or cut-price DVD players in the shops of central Baghdad. The strikes were brushed off by the military as the work of “dead enders” from the ousted regime.

Soon, the incongruous sight of American soldiers shopping or eating lunch in restaurants in body armour was a thing of the past. The bridges were lined with high chain-link fences to stop the grenade attacks. Instead, the Americans were targeted at checkpoints to their bases, between the newly built canyons of concrete blast walls.

Kamikazes in cars filled with bombs would blow themselves up as US troops searched waiting vehicles. In response the army put Iraqi security forces at their gates: an American soldier admitted last week that this was still the only effective way of protecting US troops from car bombs.

So the car bombers started ramming their vehicles into convoys on the roads. The Americans replied by shooting at any car that came near them.

By November 2003 the guerrillas had organised themselves into cells capable of shooting down helicopters. Bloody crashes followed: a helicopter with 16 soldiers going home on leave plunged into a palm-fringed field in Fallujah. The choppers started flying at night, swerving and ducking unseen missiles.

Patrols in cities were reduced and more Iraqi troops put in the streets. But the Iraqi soldiers shared bases with their US counterparts, and guerrillas infiltrated the new army. A year ago the unthinkable happened: a suicide bomber dressed in military fatigues blew himself up in a US Army mess hall in Mosul, killing more than 20.

The Iraqi forces were failing to control the insurgency and whole towns, such as Fallujah, Yusufiyah and Maadain slipped out of control. The Americans were forced to fight their way back in, losing scores of soldiers in vicious street fighting. If they stayed out of the towns they were attacked; if they went in they were attacked. They had to start training most Iraqi units from scratch.

The American vehicles gradually became more heavily armoured. It started in Fallajuh where underequipped troops would sandbag the backs of their trucks and bolt on scrap metal plates. As heavier armour finally arrived, the insurgents started using more lethal “shaped” charges, which coalition officers said were being supplied by Iranian agents. Suddenly the rocket-resistant armoured personnel carriers became rolling sarcophagi.

It has been a rapid and brutal evolution of attack and counter-measure, yet at least one American soldier is being killed almost every day in Iraq.

The toll of 2,000 remains far below the much-quoted benchmark of warfare, Vietnam, where more than 55,000 American troops died. But with polls indicating that most Iraqis support attacks on coalition troops — American and British — and with support for the war flagging back in America, the comparison with that ghost is only likely to grow.

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