CAMP LEATHERNECK, Afghanistan — It has taken the United States years to amass the mountains of gear piled up at huge bases like Camp Leatherneck in southern Afghanistan. It is the job of logistics experts like First Lt. Rachel...

http://www.nytimes.com/2012/08/04/wo...pagewanted=all

the american bases usually leave a mass of toxic waste behind, when they move on. even in america.
they did this in iraq and the local people unknowingly utilise some of the objects that are harmful to their health. the dead bodies of tanks can contain depleted uranium and i have seen many pictures of children in iraq playing on them. in afghanistan, i read, that there have been about 450 bases of varying sizes.

What did they accomplish besides death and instability.

^
Testing their weapons, awarding contracts to themselves etc.

testing their weapons against a bunch of guys with AK47s? If they wanted to test their weapons it would be against a real army like Iraqs or Pakistans.

Awarding contracts to themselves is no gain sum situation. It just transferring wealth from themselves to themsleves.