When Gen. David Petraeus took over the Afghan war effort, the conflict took a violent turn. Especially that part of the war launched from above. Petraeus relaxed the restrictions on air power, and strikes from sky returned to a level all-but-unseen since the war’s earliest days. In October of 2010, coalition planes unleashed their weapons on more than 1,000 missions.

Now, Petraeus is gone, and the air war — like the rest of the conflict — has cooled a bit from its fever pitch. In the three full months since Gen. John Allen assumed command, strike sorties are down more than 25% over the same p...