The Second Amendment is a recognition of the danger of standing armies. Its purpose is to recognize that every citizen has the right to keep and bear the same type of basic arms as a soldier in a modern military. A militia embodies all able-bodied men over the age of sixteen. Therefore, a militia will always outnumber a standing army by at least twenty to one. If this militia is armed with weapons similar to those used by the individuals comprising the standing army, it will be impossible for that standing army to inflict the will of a tyrannical government upon the people. The Second Amendment is the guarantee behind all the other articles in the Bill of Rights. It is the ultimate guarantee that citizens in the United States will remain free.
You couldn't have said it any better - I copied and sent it to myself for future reference