In essence, the 3rd Amendment of the Constitution (seldom looked at in depth), prohibiting the quartering of troops, walks alongside the 2nd Amendment's establishment of the need for a militia. It was envisioned, that when a war (constitutionally declared) was over, via surrender or treaty, that the "standing army" of that war would always be dissolved, or at least reduced in strength to mere cadre level.
Soldiers would return to their fields and farms and shops, until the next emergency, when they, already armed (by the right declared by the 2nd Amendment) would amass again to address the emergency/fight the new war. The "cadre level" would maintain bases, stay up to date on weapons and tactics, and practice managing militia mobilization.
A "large standing army" was and is anathema to American thought; americans prefer a small, crouching army (SCA) instead. This held true until FDR/Truman, armies being deactivated quite routinely between the US's wars.
With the onset of the Cold War, that changed. It being thought of as a war, though undeclared constitutionally, it seemed to justify the funding and support of a large standing army. The immediate events in Korea and, in succession, Viet Nam, Panama, Grenada, Nicaragua, Bosnia, Iraq1, Afghanistan, Iraq2... has gotten 2 generations of americans more accustomed to the idea of a large standing army being "necessary", due to the threats perceived, and the speed with which we think we need to respond to crises/emergencies.
Resulting in a situation in which the LSA (large standing army), its existence and justification, is now a foregone conclusion. To the detriment of the concept of militias.
Bookmarks