I was under the impression that we were staying in afghanistan to keep pakistan from destabalizing because of all the taliban refugees that fled afghanistan when we invaded. Obama ran his campaign on beefing up afghanistan, not ending all war. If we had to stuck to afghanistan instead of stupidly invading Iraq (a country that was successfully secular, even if it was run by an evil dictator). Now after deposing Saddam, and we leave Iraq, the Taliban will just have a huge recruiting force.
We aren't the world police, but I can understand why we are beefing up Afghanistan. We need to take the pressure off our current troops so we can focus on training the locals.
