Afghanistan used to be a relatively peaceful country with a centralized but weak government. Problems arose with the boundary with Pakistan demarcated by the British. The disputed border -- the Durand Line (after the foreign secretary of British India who established it) -- divided the Pushtuns between two countries. That left the world's largest tribal group (over 40 million strong) without a politically unified homeland.
If the war is winnable, the answer lies with the Pushtuns ....
David Isby