Oh my young Padawan; the force is weak within you son. Right from the beginning of this great experiment known as the United States of America; all men between the age of 18 and 45 were and still are considered part of a standing militia.
What has happened along the way was what we know of our standing Military funded by the federal government. Militia's still exist all over this great nation and thank God they do because one never knows when a tyrannical government might corrupt the military or any of the other armed federal forces.
This brings us to the 2nd Amendment. Probably the most important right we have because this one right protects all the others.
You sound either young, naive, or both. I hope this small history and civic lesson prompts you to learn more about both your rights and responsibilities. Being an American has both.
Ahhhhhhhhh...but you seem to forget that was before the 13th Amendment was ratified (1865), correct? These days, we choose to join the Military out of patriotism & love of country or as a career or all 3 (OK...& the life-time benefits don't hurt, either), & we are not forced to do it except in times of war when actually declared by Congress. You may be young or naive (I'm 52 & enjoyed reading The Federalist Papers & other works of the Founders before my vision went bad) but let me remind you that the 2nd Amendment respects individuals, whose rights come from God, regardless of whether they are in the Military or not.
BTW...Mr. Rogers gave me better history lessons back when I was a kid. Don't forget: practice makes perfect.