Former military and have plenty of military in my family.
The army could not organize a potato sack race in the time it would take for the militia to respond to an attack by a foreign power.
Hmmmm. I wonder.
In
Marine!, the biography of Chesty Puller, there is a section about getting ready for Korea. The regular marines got a huge number of (reservists?) organized, embarked, and on their way in a surprisingly short amount of time.
I guess one element of this conversation should be about how much advance notice you get. It seems like most of the time, there is enough notice through spies and whatever that you can begin your own build-up. Unless the government is ignoring the signs and actively provoking ala Pearl Harbor. But, that was just a fleet action, not an invasion.
Two anecdotes from the biography do highlight at least one danger of a standing military. First, the Marine rifles from WWII were put away in cosmoline without serious inspection. Puller had to personally inspect and reject a large number of them as worn out or defective after the cosmoline was cleaned off.
The second stems from his experiences in Hawaii. He was posted to Hawaii back in the 1920's or 30's and noticed that the machine guns were missing parts like asbestos gloves to change barrels. Then, about twenty years later, he was posted in Hawaii again. He noticed the machine gun maintenance had not improved.