From the Revolution until WW2, the US had a very small standing peacetime army which mainly served as a cadre for wartime forces, which temporarily expanded during wartime to a meaningful fighting force by mobilizing the organized portions of the militia (by placing state organized militias under federal operational command), mobilizing the unorganized militia by voluntary and compulsory means (radically expanding the army size for the duration of the emergency and assuring that size was filled through broad-based conscription).

That broke down significantly progressively after WWII, as the US transitioned to what is effectively a fully professional army.

The Continental Army was (mostly) formed under a "Cincinnatus agreement" that they would return swords to plowshares after the Revolutionary War. At least some of the founding fathers (and it is said even George Washington) were under the assumption that the country would not have a Standing/Permanent Army. There certainly were founding fathers that hoped the Second Amendment to be an attempt to prevent anything larger than regional/state militias from forming outside of defensive emergencies as similar "Cincinattus style" formations of farmers expecting to return home to farming once the war is over. America even named an entire (semi-)major city Cincinnati to try not to forget that war shouldn't be an industry, and warriors should stand down in times of peace. It's strange how remote an ideal that seems today in modern America.

the modern usage of 'regulate' has eviscerated much of the constitution especially the commerce clause which now days is generally interpreted as literally the opposite of its original intent