By Richard Bilton BBC correspondent in southern Iraq

Preventing the mass sabotage of oil fields was a vital coalition goal

The thing that strikes you straight away is the smell. The acrid taste of oil from the plumes of smoke that rise from the desert.

This is the Rumaila oilfield in southern Iraq - and oil wells are burning.

This was a crucial target for the coalition forces. In the first hours of the war, US Marines stormed across the Kuwaiti border.

It's an area that produces 60% of Iraq's oil and it was important to take it intact.

The fear was the kind of destruction seen during the last Gulf War. Then, retreating Iraqi troops set fire to well after well, turning the sky dark with burning oil.

Driving north across the desert, it's clear that sabotage on that scale has been avoided. Flames and smoke do scar the horizon - but only a handful of wells are ablaze.

Though many well-heads were mined or booby-trapped, the coalition's assault was too quick for them to be detonated.

'Iraq's future'

So now there is a mixed force of British and American military engineering units working in the heat and the dust. They are here to get the oil pumping again - and it's a key role.

The coalition forces believe these oil reserves are Iraq's future - a natural resource that could fund the rebuilding of the country. And it's some resource.

A US Marine on guard in the Rumaila oil fields

Only five days into the war - with fighting still going on in the northern part of the Rumaila field - oilmen are already here, predicting big things.

Civilian engineers from Houston in tin hats and red suits are working alongside the military. "In five years", one told me, "this could be the most important oilfield in the world."

But right now, it's still dangerous. I was with the first band of journalists the Americans had taken to Rumaila.

All future trips are suspended - there is too much risk. We were only 10 kilometres into Iraq, but right now nowhere in this country is safe.

'Bleak and barren'

Out in the desert - as we packed and prepared to leave - a pickup truck roared past us. On board, five Iraqis who wanted to surrender.

No military clothing and, in the end, no threat. But the guards were jumpy, the place feels edgy. Behind the forward line it's hard to know who or what you are dealing with.

This is a bleak and barren stretch of land. Nothing really here but the wells and the precious resource beneath.

In a war where oil has never been far from the debate - allied forces say they have achieved their aim.