If the enemy can mass larger forces, they can hit small units and force the government to either accept demoralizing losses or mass troops in larger formation capable of resisting larger enemy attacks. The latter means that the government security net gets thinner (but clumpier), and so the people themselves are more vulnerable to insurgents and terrorists.
In addition, by keeping the enemy atomized, we ensure that the government's forces can handle the enemy insurgents without the full array of equipment that our forces employ.
In Iraq, I rarely read of even an enemy platoon-sized attack (30-50 men). Iran and Syria may fund and help the terrorists inside Iraq but they do not allow them, apparently, to organize in their territory.
In Afghanistan, the situation is different. The Pakistanis look away for the most part while Taliban and al Qaeda mass and train in Pakistan. We can only try to atomize them when the enemy is ready and enters Afghanistan. Strategypage describes the enemy goal:
NATO commanders believe that the Taliban are planning a more aggressive operation in the Spring, using groups of up to a hundred men to attack small towns, especially local government headquarters. These towns often have only a dozen or so policemen, and some armed locals. Coming in at night, the Taliban can take over, get some propaganda videos, and have a chance of getting away before government or NATO reinforcements show up.
We must find ways to disrupt the enemy sanctuary in Afghanistan, break the enemy up as they enter Afghanistan, track and attack them as the move within the country, improve local defensive capabilities, and improve response time of reaction forces that can prevent the loss of a town or at least pursue the enemy to make sure the survivors aren't enough to take on another town's small police force.
It is a real handicap to fight an enemy that has a safe sanctuary. Hopefully it is not fatal.
