Last December, DoD released the
“Defense Science Board 2004 Summer Study on Transition to and from Hostilities” that said we "may require 20 troops per 1000 indigenous people."
Under a "worst case scenario", that could mean 480 thousand troops in Iraq and 560 thousand in Afghanistan for several years.
NOTE: The numbers are mine based upon a worst case scenario using the report’s 20/1000 factor (see below) and country populations. QUOTE
We believe the aforementioned changes are needed in DOD. However, it is not clear that even the resources and capabilities we envision will suffice if the nation continues to maintain the current pace of stabilization operations. History indicates that stabilization of societies that are relatively ordered, without ambitious goals, may require 5 troops per 1000 indigenous people; while stabilization of disordered societies, with ambitious goals involving lasting cultural change, may require 20 troops per 1000 indigenous people. That need, with the cumulative requirement to maintain human resources for three to five overlapping stabilization operations as noted above, presents a formidable challenge.
Furthermore, to be fully effective the United States will need to have some of its people continuously abroad for years, so they become familiar with the local scene and the indigenous people come to trust them as individuals—tours of duty that we imagine to be far longer than traditional assignments today.
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