Just what do we expect to gain from “conquering Afghanistan”?

From my front porch it looks like we would have to be a major occupying force for decades to come simply to keep some low level sense of security for the AF-G’s

Of course we could simply be using the entire thing as a giant war fighting exercise, continuing to feed the military industrial complex with huge contracts to research weapons for other engagements. Under those circumstances, hey, let’s just keep shoot’n ‘em up.

But I go back to my initial question.

Just what do we expect to gain from “conquering Afghanistan”?