Maj. Gen. Rick Lynch is in charge of the U.S. troop surge in the areas around the south and east of Baghdad. He has 29 patrol bases scattered across his area of command, and he worries about every one of them.
"Three of them have been attacked already by the enemy trying to do a catastrophic attack," he says. "If they were to do that and kill a bunch of Americans, that would influence the debate back in Washington."
In June, a guard manning a machine gun at Patrol Base Warrior Keep on the Euphrates River saw a truck make an abrupt turn and head for the base. He shot at the driver and stopped the truck. It had 14,000 pounds of explosives inside -- enough to level the whole base.
As the political debate over the troop surge and the war in Iraq continues to rage in Washington, military commanders on the ground in Iraq are intensely aware that everything that happens in Iraq could tilt the balance of the debate back home.
One of their main fears is an attack that kills a lot of U.S. troops. But as the troop surge pushes more Americans into smaller bases so they can have more contact with local people, the danger of just such an attack goes up.
"Force protection" is the term commanders use for all the measures they take to protect the bases. Cameras are put up on masts around perimeter fences to give early warning of a hostile attack. Concrete blast walls shaped like an inverted "T" to deflect any explosion upwards are installed around entry and exit routes. Guard posts are manned constantly. And the soldiers attempt to get locals to trust them enough to pass on tips about insurgent activity.
So far this month, U.S. casualties have actually gone down. With three days left in July, 67 Americans have been reported killed so far in Iraq, compared to 101 in June and 126 in May.
But the commanders are not complacent, and many fear al Qaeda may be planning the equivalent of the 1968 Tet offensive in Vietnam -- a series of surprise attacks that decisively turned U.S. opinion against the war.