President Obama is right to insist that U.S. military leaders produce a reasonable strategy for winning what he calls the “war of necessity” in Afghanistan. But judging by Army Gen. Stanley McChrystal’s memo describing the results of his review of the situation in Afghanistan and Obama’s comments over the weekend, it remains unclear exactly what “winning” means. This is no small thing because it is impossible to have a strategy when you don’t know what victory looks like.

Obama says the United States remains in Afghanistan eight years after 9/11 “because al Qaeda killed 3,000 Americans and we cannot allow extremists who want to do violence to the United States to be able to operate with impunity.” That means preventing the establishment of a government in Afghanistan that would give al Qaeda freedom of movement, which is what they had when the Taliban controlled Afghanistan before the U.S. invasion in 2001. So, winning means defeating the Taliban and establishing a government in Afghanistan strong enough to prevent a Taliban resurgence once the U.S. withdraws its forces.