You might want to check out a book called The Village by Bing West, about a small Marine CAP (combined action platoon) that was tasked with helping local Vietnamese secure a village from VC predation. The Marines and the militia "officers" occupied a small, fortified base camp from which they would launch frequent patrols. The rest of the militia forces would live in the village when they were off duty. Once again, active defense was a key part of the overall strategy.
I could see a similar approach being taken in the T2K world- a small unit of professional soldiers teaming up with a small local militia force to provide security for a small-ish settlement (hamlet, village, town).
For a larger settlement, if it's in or on the periphery of a military cantonment area (home to a division or larger), it's probably going to be garrisoned by a part of whichever larger unit calls the area "home".
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