In the winter of 1951, President Dwight Eisenhower reluctantly allowed the French army to employ American napalm against the Viet Minh at the Battle of Vinh Yen. The effect was electric. Enemy soldiers were petrified:

"The bomb falls closely behind us, and I feel its fiery breath," a Viet Minh officer recounted in a diary passage quoted in Bernard Fall's history "Street Without Joy." "The men are now fleeing in all directions. ... I stop at the platoon commander ... his eyes were wide with terror. 'What is this? The atom bomb?' "

In a short time, however, the psychological impact of the pyrotechnics of burning gel waned. To the Vietnamese, napalm became just another kind of bomb, deadly and destructive to be sure, but no more frightening than any other air-delivered weapon. The French increased the use of napalm in subsequent battles, but by the time the French army surrendered in 1954 at Dien Bien Phu, the Viet Minh had learned that napalm, like all air strikes, could be avoided through concealment, dispersion and entrenchment.

Right now, the Islamic State is going through this same evolutionary process along the western border of Kurdistan. As one can see from the grainy black-and-white "gun camera" tapes released by the Pentagon, the U.S. air strikes of the past week have mostly succeeded.

Lazy and overconfident Islamic State forces positioned their artillery and mortars in the open. Their convoys were bunched together and tended to travel along established highways, where they could easily be spotted by drones. As planes approached, fighters cowered in fear or ran away.

Expect them to learn quickly from these mistakes. Many Islamic State commanders are former Baathist officers who have seen U.S. firepower in action and understand how to respond to it. Some are veterans of almost three years of Syrian bomb strikes and are comfortable with quickly taking cover at the first sight of aircraft overhead. Recent images show they are dispersing their newly acquired U.S. tanks, Humvees and artillery. They also are beginning to hide their command posts in villages and digging in their small units. Their supplies are being stuffed into houses, where they cannot be spotted from the air. It's an old tactic that works. Just ask the Israelis.

Recent history suggests there will be strategic consequences from seeking to blunt the Islamic State advance through air power alone. First, the effectiveness of pinpoint strikes will diminish quickly; it generally takes only a few weeks for a disciplined force to become inured to the psychological effects of such firepower. Second, as the enemy becomes harder to kill, a greater investment will be needed to get the same results. Soon "targeted strikes" by only one or two aircraft will become meaningless, and more bombs will be needed.

Third, as targets get harder to locate from the air, it will become necessary to push ground reconnaissance units forward to find and flush Islamic State units into the open. This task will involve greater risk not just to Kurdish pesh merga fighters, but also to U.S. special forces units that must accompany them.

Fourth, as we increase our killing power and the Islamic State retreats into towns and cities, images of dead children - and questions of moral proportionality - will emerge in the global media. Eventually, terrible as it is, the Islamic State narrative will begin to trump the U.S. narrative. When that moment arrives, we will have no other option but to turn the aircraft carriers around and go home.

Fifth, and most frightening, would be the terrible consequences of the Islamic State's managing to shoot down a piloted U.S. aircraft. Remember, these are clever and well-equipped soldiers who have downed many Syrian fighter jets over the past three years. Terrible images of a captured U.S. flier on an Islamic State website would inflame the conflict.

The bottom line is simple. In a firepower approach to war, escalation and mission creep are both inevitable and necessary. As the enemy grows more skilled, we will be left with two unattractive alternatives: Escalate until tragedy occurs or accept battlefield stasis until the American people tire of these "targeted strikes." And when we fly away with the Islamic State still dominant on the battlefield, the terrorists will proclaim to the world that the United States is a cowardly country that has been beaten again.

Robert H. Scales, a retired Army major general, is a former commandant of the U.S. Army War College.