THE BOMB

The attacker had buried the explosives -- probably a 155-mm artillery shell -- in a hole just off the pavement, on the east side of the highway's northbound lane, next to a short concrete pillar.

The wire to the detonator stretched from the bomb under the sand, into a field of grass and shrubs and a few trees. The wire zigzagged all over the field, ending behind a dirt berm, about 50 yards from the road.

The berm was good camouflage. Standing behind it, the bomber was mostly hidden, but had clear sight of the convoy of big rigs rumbling up the highway, and the American Humvee in the lead.

When the Humvee reached the concrete pillar, the truck was in line with the bomb.