I have a traditional quasi-medieval fantasy realm where a few generations back improper use of magic lead to creation of monsters throughout the land. Our main countries have had to figure out how to hold, or reclaim, land back from these monsters in order to thrive.
The Kingdom solution was to train up highly skilled soldiers to fight and drive back these monsters, and while they suffered loses from this it's worked relatively well. However, the other major country, the republic, had monsters that are naturally stronger, due to being closer to the epicenter of the disaster that created them in the first place, than those faced by the kingdom, strong enough that attempting to fight them off directly would lead to heavy casualties.
Instead the republic's solution has been to jeryrigg older magical devices, originally used for communication between settlements like a magical telegraph, to create a sort of magical resonance that is annoying to monsters. While not directly harmful to them it caused enough distress to discourage monsters wandering too close to settlements. In addition to this, every settlement has militia trained with a sort of magical musket that can take potshots at any monsters that get too close. These shots degrade in damage done the further away from a target they get, so at maximum range from the monsters (the closest any militia member wants to get) they do little damage, but the pain of being shot, combined with the general annoyance of the jerry rigged communication device, is generally enough to discourage monsters from wandering too close to settlements.
What I need to explain now is how merchants and caravans successfully travel between settlements. Since the monster annoy-o-tron devices are based off of previously-made magical devices, which the republic can't create from scratch anymore, there is a limited number of them, basically one per settlement prior to the magical collapse, and settlements are not going to willingly give away the only device that keeps their settlements safe. I'd also imagined these devices being bulky enough to not be easily transported. This means that caravans between settlements won't have the magical protection to discourage monster invasion. They can still shoot at monsters with rifles, but I'm not convinced the pain of the rifle pot shots alone would be enough to keep monsters from attacking when humans 'invade' their territory.
In theory the monsters could be fought and killed, but these monsters are supposed to be strong enough that only a very small number of elite fighters would stand a chance of defeating them, again I'm not sure it's reasonable to expect every caravan to have such skilled solders to defend it. I intentionally want the republic's available solders to be less skilled compared to the kingdom's so that the kingdom would look to have an advantage when they invade, as such I don't want to imply there is a large standing force of elite mercenaries used to guard caravans which could be drafted in time of war.
No one uses magic any more, it has a significant stigma against it after the last disaster. The republic does have a few devices that work like magitek, but they too are limited and not fully understood. This limits the availability of a magical solution to protecting caravans.
What other tricks could I use to make it possible for people or goods to travel between settlements safely? I'm okay if travel is harder due to monsters, or limited to only large caravans or otherwise require more logistical overhead to do safely, but I need some means that it can happen.