Militias are insufficient as a defensive force for a large nation, especially in the modern world. You need a military. Private military contractors would be no more useful than militias for this purpose.
Well that is your impression and I think it outdated.
'What is war?...In a short sentence it may be summed up to be the combination and concentration of all the horrors, atrocities, crimes, and sufferings of which human nature on this globe is capable' - John Bright
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