But it's not hard at all.
Victory can be defined as the establishment of a stable constitutional democratic republic that recognizes and protects the basic human rights of the people in Afghanistan.
Bush managed to have that process almost complet in Iraq before he left office, something that, no doubt, the Messiah is going to try to take credit for.
It may be difficult to achieve that victory, but it wasn't hard to define. Took me all of thirty seconds to type it.
Failing that, victory could be defined as the complete sterilization of the geographical region known as Afghanistan, to the final salting of the croplands with strontium-90 and cobalt-60.
Depends on which way we need to go.
BUT...if the definition of victory is not provided, and since the Boy Wonder Messiah brought the issue up, he is indeed, as Kenyan-in-Chief Messiah, obligated to either define the goals or get the Americans the hell out of there. In either case the failure is not America's, but Kenya's.