I personally expect that at the time of the pole shift most countries will be under martial law. To impose martial
law within the US to the extent that is now technically already in effect, but being held off in the implementation
would place troops in virtually every community. In order to do this the regular military would have to be
augmented by the entire National Guard and the entire Reserves. In addition, vast numbers of the regular military
that serve in such ways as tank, artillery, and special munitions companies along with over 20 times that number
which serve to support them would have to be reassigned to MP units for which they aren't trained.
In most communities you are looking at an inexperienced second Lieutenant in command of a platoon or even just a squad of 17. Even in a city under control of a Brigade, the commander isn't likely to rank higher than a Lt. Commander. I know these people! They have families, go to work and come home in the afternoon, and have barbecue on the weekend, just like other people with day jobs. Their mind set is to go to War; not to bully the helpless. The soldiers are kids not old enough to buy a six pack of beer in most states. 99% of them have never even actually seen an LA gang member, much less ever even thought about hurting anyone except in the context of War where they are being shot at.
The most likely scenario for the vast majority of these units will be a very quick realization post pole shift that there is no longer a government to serve and they will be attempting to get back to their loved ones. Should their loved ones be located somewhere that obviously has been destroyed, they will be looking to assimilate into communities. And I expect that they will be welcomed by communities for protection from the few inevitable groups who will be attempting what you outline.
Offered by Ron.