At the time of the American Revolutionary War, militias were groups of able-bodied men who protected their towns, colonies, and eventually states. "[When the Constitution was drafted], the militia was a state-based institution, Well-regulated in the 18th century tended to be something like well-organized, well-armed, well-disciplined. "It didn't mean 'regulation' in the sense that we use it now, in that it's not about the regulatory state. There's been nuance there. It means the militia was in an effective shape to fight.

What type of security was referred to here? To get to that, consider the climate of the United States at the time. The country had just fought a war, won its independence and was expanding west. There were plenty of reasons to feel unsafe, and so "security" had a very palpable meaning. "You have an expanding country, and the principle defense use of the militia would be to protect local residents from attack and invasion It also meant physical protection from government overreach.

The idea of a state militia would also be attractive because it serves as a deterrent against national tyranny," says Rakove. "At the time, if government forces tried to take over land or overstep their boundaries, you'd have an institution in place -- the militia -- that would outnumber any army." Of course, with the size and scope of the modern United States military, and the fact that militias as we know it no longer exist, that notion is hard to imagine today. In the debate over the Second Amendment, this phrase, "a well regulated militia," remains one of the most cited and argued parts of the sentence.