Actually, with just a small amount of research, you will find EXACTLY what the two classes of the militia really are, and you will find that the Founding Fathers did not want and did not authorize a standing Army.
In fact, according to The United States Code, it is very likely that YOU and YOU and YOU and I were members of the United States Militia! I knew I was a member, did YOU? If you are between the ages of 17 and 45, and a male citizen of the United States, you might want to investigate YOUR obligations as a member of the Militia! Start with Title 10, United States Code.