This rule always applies—except during emergencies, as when the guy on the ground is being overrun and says, “To hell with it, my only hope is for air to bomb my position. Maybe the enemy soldier with the knife at my throat will get hit instead of me.”

The area between the FLOT and FSCL defines close proximity, meaning that if you are attacking a ground target between these two lines, you are doing close air support and are by definition in close proximity. On the other side of the FSCL, any military target could be hit.

The FSCL is usually placed where it makes sense. For example, in a static situation where neither side is moving on the ground, a good place to put it is somewhere near the outer range of friendly artillery along some clearly recognizable feature, like a line of hills. If the ground forces are in the defense and expecting to fall back, you want the FSCL quite close to the FLOT, so you can attack the enemy ground forces with the least restrictions as they mass for the attack. If friendly ground forces are attacking and moving forward, then the FSCL should be reasonably far out, because of the greater risk of hitting your own troops as they overrun the enemy.

To accommodate the rapid advance we expected during ground operations, the land forces and airmen had arranged a whole series of “on-call preplanned FSCLs”—lines on maps that could be activated as the attacks progressed. Thus, if one corps didn’t move forward as fast as expected, its FSCL would remain close to the Saudi border. If, on the other hand, the adjacent corps moved faster than anticipated, its commander could push to the next preplanned FSCL (or at least the segment in front of his FLOT).

During the nine hundred hours of war that preceded the ground offensive in Desert Storm, the FSCL was the border between Saudi Arabia and Iraq-occupied Kuwait.

First, there were no friendly ground forces north of that line (except for a few Special Air Service and U.S. Special Forces hunting Scuds, and we had special measures in place to protect them). Second, there was a bulldozed berm marking the frontiers between Saudi Arabia and its neighbors to the north. Every pilot could easily see if he was over friendly forces or the enemy.

Who decides where to put these lines?

Since the FLOT is determined by the actual placement of friendly forces, you simply find out where your own guys are and draw a line on the maps.