if the military Commanders decide to ignore their oaths to the Constitution which the CiC already has, and turn the heavy weapons of the military on its Citizens then the Country is lost. Mass murder of Citizens is the act of monsters the like of Hitler, Stalin, Amin and dozens of their ilk. However, even Hitler and Stalin disarmed the populace before turning the military loose on the citizenry.
With only pistols, to start, the Poles of the Warsaw Ghetto held off the SS for so long Hitler finally just had the Warsaw Ghetto burned to the ground rather than try any longer to suppress the Ghetto.
Yes, with small arms you cannot stop a major military, but although they can kill you, they cannot defeat you.