IEDs: the insurgents’ deadliest weapon

What exactly is an IED?

The term "Improvised Explosive Device" refers, loosely speaking, to any jerry-rigged bomb dating back to the Gunpowder Plot. But since the invasion of Iraq in 2003, it has come to describe the lethal variety of roadside, truck-mounted and suicide bombs used by insurgents against coalition forces and Iraqi and Afghan civilians. The devices, hidden in potholes, amidst rubbish and even inside animals, have accounted for around 70 per cent of America's 4,207 combat deaths in Iraq and wounded more than 38,000 US soldiers. IEDs have also accounted for 100 of the 235 British soldiers killed in hostile action in Iraq and Afghanistan.

But haven't IEDs been used in other conflicts?

Certainly. In WWI, T.E. Lawrence used railway and roadside bombs to disrupt Turkish supply routes and create, as he put it, "an uncertain terror for the enemy". Belarussian guerrillas used IEDs in WWII to derail German trains. In Vietnam, IEDs caused a third of all US casualties; in Northern Ireland the Provos made wide use of IEDs, from simple petrol bombs to more sophisticated remote-controlled devices, such as the 1984 Brighton hotel bomb. What marks them out in Afghanistan and Iraq is that they have become the "signature" weapon of the conflict.

Why is the IED regarded as the "signature" weapon?

Because of the extent and effectiveness of its use. In Ulster, British troops encountered 7,000 IEDs in 30 years of conflict. In just four years of conflict in Iraq, from 29 March 2003 - when four US soldiers, searching a taxi at a checkpoint near Najaf, were blown to bits by 100lbs of C-4 explosive in the boot - to mid-2007, there were 81,000 IED attacks. Such attacks have been rarer in southern Iraq, where most UK forces are stationed, but are ever more prevalent in Afghanistan. There were 22 in 2002; between April and June this year, there were more than 200. The Pentagon, which this summer reported more than 100 attacks per day, calls the IED "the single most effective weapon" used against the coalition. "It has levelled the battlefield in favour of insurgent and terrorist groups," says ex-CIA man Robert Baer.

Why have IEDs proved so effective against the coalition?

Partly because they're cheap, simple to build, and, given their limitless variety, hard to spot and defend against. But also because they are so strategically effective. They don't just maim and kill coalition soldiers; they make every civilian a suspect, every car a possible bomb, and drive up hostility against the local populace. The massacres of Iraqi civilians by US marines in Haditha in 2005 and by Blackwater, the security firm, in Baghdad last year both followed IED attacks. Like booby traps in Vietnam, IEDs are a symptom of a broad-based insurgency. "The IED is the enemy's artillery system," says US general Montgomery Meigs. "They didn't come through three-dimensional space in a parabolic trajectory. They came through a social trajectory and a social network in the community."

How are IEDs made?

"All you need is a battered old car, a couple of hundred pounds of homemade explosives and a detonator," says