Since we have always been fighting Pakistan in the war in Afghanistan, (by this I mean they have been providing an endless supply of manpower and armaments to the Taliban for 30 years now), we should either just pull out of Afghanistan because the war is unwinnable; (because we cannot attack Pakistan) or just nuke Pakistan and get it over with. We didn't win in Vietnam because we were afraid to takeover North Vietnam with an invasion; because we were worried we would get in a war with China. China was providing all the munitions and armaments to the North Vietnamese. For this reason we should have left Vietnam in the 1960's since that war was unwinnable also;(because of the limitations we were placing on ourselves).Unless you attack and destroy the proxy country or countries providing all the manpower, ammunition and food in a war you will never win it.