The Garrison Towns were the few somewhat bigger settlements on Arrakis northern hemisphere.In contrast to the poorer Pyon villages of the Graben, Sink and Pan -folk, here most "outworlders" lived. These towns were fortified, against "Fremen riffraff and sand pirates", Smugglers and the occasional daring Offworlder Razzias.
The Garrison towns not only housed most of the Military and Mercenaries but also Technicians, beaurocrats and Spice mining facilities, though the best Dune Men, Sand Workers, Spice drivers, Sandmasters and Spice-hunters still came from the Pyons and were often at good terms or even distantly akin to the more northern and sociable Fremen.