Why is an outside military needed to train a country's military on fighting rebels? If the rebels are so effective against government troops, could it be that the government troops are either unmotivated or corrupt? In the case of Afghanistan, why has it taken 12 years to train Afghan troops in counterinsurgency. Shouldn't those who were trained 12 years ago have enough expertise to train others? Consider that many of the outside trainers had no military experience at the outset of the war in Afghanistan.
From what I've read, the Afghani soldiers are in it for the money, honest or otherwise, or because they were drafted. Too many of them have no loyalty to the government.
I think U.S. policy long ago should have been: Karzai! Shape up or we ship out!
See also “Insurgencies, outside forces, and good government”.