I wasn't trying to be rude, I was just geniunely curious. I would suggest that your course is a stepping stone, there is a lot of information out there about what happened in Afghanistan during the Reagan era. Noam Chomsky might be a good author to start with.

Once you look into it a bit further you will see why America kept going back for more, as you put it. It wasn't because of some sort of humanitarian desire to see the people of Afghanistan safe and sound, that's for sure.