Very true, Stratiotes, however the logistical challenges of invading the continental United States (as well as the sheer size of the place) make this sort of problem very unlikely for us. The problems we do have, however, are bad enough as it is.

For example, it takes a long time to train a professional infantryman. Light infantry are the backbone of any small war effort, and infantry are mandatory for the big wars, too. I worry about our nation's ability to handle a truly major theater war - something on the scale of the US Civil War and the two world wars. The fact that we don't have an enemy on the horizon doesn't mean this kind of thing won't happen again - history shows us that it likely will. We had several million men under arms in the last big war - and that was with a much smaller population. How will we put a twenty million man army together? Militia offer up something of an answer - a big body of part trained men who will take to soldiering better than totally untrained recruits. To my mind, they should focus on five skill sets and ignore everything else: 1) Physical fitness 2) Marksmanship 3) First aid/emergency medicine 4) Night operations and 5) Squad level tactics of the most basic sort. By concentrating on a few fundamentals the militia can remain competent at the most basic job - higher level training will come when and if they need it.