Public vs Private - MILITARY

It is surprising that in all my years, I haven't seen an Economist article debating whether defence forces should be privatised and to what extent. Klaus Rohde touches an aspect in Private wars. In my own experience the first time I really thought about was after reading "Green Mars" (Kim Stanley Robertson) a future history novel in which the security arms of multinational companies became huge private armies. Two questions I ask myself are
- What examples of private armies in the world have been shown to be more effective than the standard sort? and
- Should we presume that privatised armies will allocate resources more efficiently, and therefore be more cost effective, or even decisive in situations where resources are subject to extensive competition?

The standard analogical analysis by the Economist leads one to believe that it is more efficient to list those things which shouldn't be privatised because it is a very short list.

As an answer to my first question, a small army of terrorists (these are almost exclusively privately run but funded by sponsoring Governments) can often "defeat" (ie. send packing to go home) a much larger, modern conventional army. I would expect that private "security" companies may have greater success at sticking out a long protracted conflict, and at a much smaller cost in say Iraq.

As an answer to my second question, there is extensive competition for human resources in a conflict situation. These are allocated much more efficiently in a terrorist organisation than in conventional armies. Western world organisations don't seem to be in the market for humans who will readily give up their life to kill for political reasons, but perhaps private security organisations from those countries are recruiting from the same pool of "brave fanatics".