Obviously the billions to be made rebuilding cities by the banks of the forces of goodness and freedom is a definite incentive. Not to mention multi-national oil companies which will help rebuild these countries. Sure you might use chemicals like Agent Orange to defoliate entire forests so you can get at the enemy for similar reasons, but that's a small price to pay for the forces of freedom and goodness to prosper.
But what about real solutions? How about not starting wars and creating power vacuums and minding your own business. But you say war is our business. And I can't help but nod and agree.