Afghans can't be pacified, the whole country is just an area of land and not what anyone could call an actual country, its like this due to the way people are who live there, tribal and insular with loyalty people in other coutries would show to their nation only shown to the tribe, tribal associations are only of convienience through marriage, financial deals and mutual protection form other tribes or groups. The arrangements fall down for the most simple reasons and can never be relied on.
You do realise that the vast majority of the people in Afghanistan do not need to be pacified don't you? Most of the people who live there are just like me and you normal people who want to get on with their lives, it is just unfortunate for them that the country was first used as a proxy war bettween America and Russia then after the Americans abandoned them there country was over run by the Taliban most of whom didn't even come from Afghanistan. Finally America decided to return to hunt down Osama who again isn't an Afghan and when the people finally thought they were free of the Taliban the American abandoned them again to go and fight a war in Iraq.
The people of Afghanistan are not iherently violent, they are just incredibly poor and unfortunate enough to have been used as pawns in a number of bettles that don't really interest them.