The Second Amendment states: "A well regulated Militia being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Recently, two contributors to the News Tribune Opinion page, one an AR-15 owner and the other a retired Air Force lieutenant colonel, attempted to explain the Second Amendment without citing any documented evidence to back their claims that it's for self-defense, to overthrow tyranny, and to repel invaders. Such explanations are popular with many gun enthusiasts.
Being a gun owner but skeptical about such explanations, I wanted to be more informed before responding. I found Thom Hartmann's book, "The Hidden History of Guns and the Second Amendment." It cites historical references, including records of the states’ conventions when they considered adopting the Constitution following the General Convention in 1787. It shows that the framers of the Constitution didn't consider defense of oneself or for "hearth and home," overthrowing a tyrannical government, or repelling invaders as reasons for the Second Amendment.
The book shows the Second Amendment was drafted to guarantee states the authority to maintain and regulate their own militias because slave-owning men like “(Patrick) Henry and (George) Mason wanted southern states to preserve their slave-patrol militias independent of the federal government.” (Note: the words in quotes are from Hartmann's book).
The Second Amendment was approved in 1791, and until the Civil War such state militias were maintained through conscription of free white men for slave patrols to put down slave revolts, to recapture plantation owners' escaped "property," and to take land away from indigenous people to give to the settlers.