I'm thankful you're not my history teacher.
Our right to keep and bear arms was meant to protect us from our own repressive government. At the time we were British colonies and had no say in our government.
The Second Amendment was to insure government by the people in the future.
Our rights to keep and bear arms are for the same reasons today. They protect us from attack from outside or from within, such as our own government or armed forces gone berserk.
Who knows, this could happen.
You didn't pay attention to your history lessons. Our Founding Fathers were and still are right on.