Surely there's a difference between the folks just doing their national service, and the career soldiers (who are the people likely to start a coup)?
In actual coups, it's often a small cadre of well-connected higher officers who do the work. It's not the whole military. By the time the whole military (or country) realises what's happened, it's already happened and there's not a lot they can do.
The career soldiers are recruited from people doing their mandatory military service, and upon this, many people having done their mandatory military service are part of the home defence and practice now and then.