Modern air war was so deadly that even the slightest mistake was catastrophic. In other wars, if you bombed a friendly position or vehicle, someone might be killed or wounded. In this war, if we mistakenly unleashed our deadly guided weapons or fragmentation bombs on a friendly position, everyone in the vicinity of the attack would be killed. Airpower had grown too deadly for the mistakes one expects in the fog of war. I knew such mistakes would happen; they always do; and they had—during the battle of Al-Khafji, an A-10’s errant Maverick missile and bombs from A-6s had killed Marines and Saudis on the ground—but I wanted to make sure we had done everything within our power to prevent more.

Thus, I gave an “if in doubt, don’t” order. And I had challenged everyone on the staff, especially the tactics team headed by Lieutenant Colonel Joe Bob Phillips, to figure out ways to avoid hitting Coalition ground forces, and a number of measures, rules, and guidance had been worked out between the Black Hole planners and the BCE.

The factor that drives our approach to close air support is not what one might think. Though bombing or strafing of enemy positions is certainly important, the chief aim of CAS is to avoid bombing and strafing our own forces. We do this by establishing boundaries, using ground references to guide our operations.

The first such boundary is usually called the Front Line of Own Troops, or FLOT (though there are other names for it, such as FEBA, Forward Edge of the Battle Area). Whatever it’s called, the concept is simple: Your guys are behind a line (the FLOT), and ahead of them is a no-man’s-land or else enemy. You don’t drop bombs behind the FLOT.

A second line is called the Fire Support Coordination Line, or FSCL, pronounced “fissile.” Between the FLOT and the FSCL are enemy ground forces opposing your own ground forces. If you drop a bomb in this region, you stand a good chance of killing an enemy soldier.

The complication comes because of the fluid nature of warfare. That is, the close air support pilot wants to make sure there are systems and procedures that let him avoid hitting friendly soldiers who have advanced since the FLOT/FSCL lines were determined. Thus the role of forward air controllers, and the rule “When air operates in close proximity to friendly ground forces, it must be under the control of a forward air controller.” A FAC is an airman who is in contact both with the ground commander and with the CAS aircraft, so he understands what the ground commander wants done and can convey that to the pilot, while making sure the pilot does not mistakenly attack friendly ground forces.