The nations’ Militaries

I have been following the developing world militaries and their history for a long time and although not an expert have read extensively on them and don’t figure out how a nation’s military can stage a coup and suppress their own people but are unable to defeat foreign armies. Why is it that the military becomes a lion for its own people but becomes a chicken in the face of foreign onslaught? Why do they need so much hardware when they cannot or will not use it against foreign aggression rather than use it against their own people? And other thing is that even when the military has not engaged in foreign wars, their leaders still reward the soldiers with medals and distinguish honors when all they have been doing is sitting on their butts. And they know who I am talking about since if they look a little closely they will see their own image in the mirror. I am not an expert on military affairs but believe that a military’s job is to secure a country’s borders and deal with internal threats if called for but not to govern and rule over their own people since they cannot both govern and rule at the same time. The more they are involved in ruling their own people, the more corrupt they become and they get involved in things which weaken their ability to fight foreign aggression. So the conclusion to all this is that they should stay out of government and politics and concentrate on securing the borders.