If you are trying to repel the advancement of an invading army, you as an individual citizen would not be facing off against the entire army inclusive of every soldier. The invading army would not be moving as a large block of soldiers shoulder to shoulder in lines and rows. In other words, as an individual with your gun in hand, you may only have to deal with one or two soldiers in your immediate vicinity. Also, when a sizable number of gun-wielding citizens converge to repel an invading army, they will have formed their own army. Then you would have one army pitted against another army.
When things get bad OUR childre will ask their families and the God of their families for guidance.
And THEN they will NOT fire on their loved ones who protect freedom. They will instead support and defend the CONSTITUTION of the United States; not the statist, elitist powder puffs who buy their way to positions of leadership.
They will not fire on their fathers and brothers and uncles and cousins. Instead, they will join them. And then the army of the enemy will be the army of the freedom fighters. The tanks and the planes and the missiles will turn to target the oppressor, not the oppressed.