Second Amendment is About Self-Defense...against tyranny or foreign invaders.

What the Second Amendment really is about is insurance.  It is the most valuable insurance clause on the planet. It says that if you attempt to invade us, you will you have a big problem with an armed citizenry.  Take a look at the historical example with Japan and their likely fears of what would happen if they invaded the mainland of the United States (assuming they could ever had overcome the logistical and troop number problems).

Our troops in Okinawa, Japan on the eve of a main island invasion had to worry too but about a different armed citizenry.  The emperor was telling his subjects that they would be killed by the American invaders and to use pitchforks, shovels or whatever they had to defend themselves. Previously, before they were backed into the corner of what was remaining of their empire, the Japanese military knew better than to invade the west coast.  They would have had to worry about firearms hidden behind every door. America’s love, obsession, respect, or fetishism with firearms is a great warning sign to any potential invaders: Have gun, will travel….so you shouldn’t.

The self-defense concept within the Second Amendment also applies to our own government. It is an insurance policy making martial law or tyranny very unlikely. Of course, an armed militia of citizens can also lead to tyranny of the majority or mob rule, so we have a very delicate balance.