The Constitution for the State of Indiana (Article 12 Section 1) sheds some light on the historical setting for how a militia is defined before it ever became so politically polarized.
Section 1. A militia shall be provided and shall consist of all persons over the age of seventeen (17) years, except those persons who may be exempted by the laws of the United States or of this state. The militia may be divided into active and inactive classes and consist of such military organizations as may be provided by law.
(History: As Amended November 3, 1936; November 5, 1974).
Section 2. The Governor is Commander-in-Chief of the militia and other military forces of this state.
(History: As Amended November 5, 1974).
Section 3. There shall be an Adjutant General, who shall be appointed by the Governor.
(History: As Amended November 5, 1974).
Section 4. No person, conscientiously opposed to bearing arms, shall be compelled to do so in the militia.
All that being said, as I pointed out before, the right to keep and bear arms is not limited to an individual's participation and place within a militia. The right to keep and bear arms predates the Constitution and the 2nd Amendment by decades if not by hundreds of years.