I can tell anyone how it was meant from history. Davy Crockett, in his memoirs, tells how he and the men of his county had decided to answer the call to help out Jackson in the Indian wars.
They took their muskets and joined General Jackson’s army for a three month stint. Jackson supplied the powder and shot.
The first part of the amendment is an introductory dependent clause, explaining the main clause, which states that the right to bear arms shall not be infringed, and in the case of the men of that time, their arms were the same as the regular army issue.
“He prefers David.”
Madison wrote, in the Federalist Papers (federalist 46 iirc) that basically the militia is everyone, that if we are attacked we can only field about 25-30,000 professional soldier, but there were over 300,000 gun owners that could be the militia if they needed to.
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Our constitution forbids a “Regular Standing Army.”
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