In a good overview of the fight and problems in Afghanistan, one analyst concludes:
The fighting in 2015 served as a test for Afghan forces, one they largely passed; however, without adapting to lessons learned, 2016 could see further gains by insurgent forces, and possibly the total collapse of an Afghan province, Helmand. Afghan forces will need to prioritize territory, abandon checkpoints, re-organize, and successfully incorporate new technologies if they wants to maintain the status quo.
The problem is that "prioritizing territory" conflicts with "abandoning checkpoints."
Counter-insurgency requires you to spread out to control the people.
For friendly people, this allows you to protect them from the enemy and recruit them.
For hostile people, it allows you to separate them from the insurgents and prevent the enemy from recruiting those people.
So a strategy that prioritizes territory--that is, controlling the territory (and the people there)--cannot abandon the checkpoints.
Yet I've mentioned that the continuing presence of checkpoints gives the enemy opportunities to mass forces to wipe out isolated outposts.
So if the Afghan security forces don't abandon the vulnerable checkpoints, their ground forces will lose morale and erode.
But abandoning the checkpoints gives the enemy terrain.
The real problem is that because we withdrew our capabilities, the enemy can mass forces to hit the small government checkpoints. And the Afghans don't have their own replacements for our capabilities.
A combination of air power, recon, and aggressive use of Afghan ground troops to go after the enemy and keep them from having the time to pick off Afghan checkpoints and deny them the ability to mass forces is the key.
This is the issue of "atomizing" the enemy, as I often spoke of during the fighting in Iraq.
This requires the abandonment of checkpoints in some areas--as we announced--to build up mobile forces that can go after the enemy to atomize them and make it safe to reestablish checkpoints to control territory (and people).
Ultimately, Afghan security forces need a balance of checkpoints with air power and reaction forces on call to help repel attacks; combined with offensive operations that reduce the ability of the enemy to conduct sizable offensive operations by pushing them down the escalation ladder to terrorism and random mortar or rocket attacks rather than the big assaults now being carried out.
Our help is key to allowing Afghan forces to adapt and succeed in 2016.