AP Photo

Out into the attack with the Royal Marines last year, we drove in dust-choked Viking armoured vehicles through the sand desert and to the crest of a ridge that overlooked the lush, irrigated valley along the Helmand River known to the soldiers as the Green Zone, their battlefield. Then, in the landscape below, people began to run. Men on motorbikes went from house to house to announce the battle. In all directions spread a panorama of terror, as women, children, boys, anyone not fighting, ran for safety. The Americans call this the "blue stream" - the indicator, almost every time, of an impending engagement.

Two days later, I was in another Viking, clutching some bit of metal in an attempt to anchor myself as it charged back to base across a poppy field. There were little grey...