A well regulated militia was designed for a time when there was no standing army. That's another reason why there is so much confusion over the wording, we live in a very different time, and having a well armed civilian militia ready to be conscripted into a military force (using their own weapons) was a necessity for national defense, not just individual liberty. As I've pointed out many times before, if China were to start an invasion of the US tomorrow, they would be repelled by the civilians in L.A. There are more guns in private hands in the LA area than in the hands of the Chinese military.
That was the reason behind the 2nd Amendment, and why it was worded that way. "To defend our country in the absence of a standing army, we must allow the civilians to arm themselves to serve in the army when it is assembled". Yes, it was also discussed that the armed people could rise up, but it was never considered in a time when standing armies were the norm.