Gallows and rope work.
Mass hanging of native Indian guerillas, Dakota territory, 1862
The way you deal with guerillas hiding amongst the civilian population is to hold random civilians responsible for any acts of resistance. A slogan is written on a wall? That’s one hanging, we’ll draw lots. Our soldier is wounded by a guerilla? That’s ten hangings, we’ll round up a place of industry we don’t care about.
Our soldier was killed by guerillas? You guys don’t learn, do you. A hundred hangings and can you direct us to the high school please?
It won’t make you popular amongst the public, but if you treat them well if they don’t rebel and regularily feed them they’ll come around.
That’s the mild approach, practiced by Nazis and others. It sometimes works.
The harsh approach is to fully control food supply and distribution. If there is any rebel activity the food doesn’t get delivered. There is a famine and it’s not until they either starve to death or hand over the rebels that they get fed. This was used by most colomial empires, British were notorious for this in India. It works like a charm though.
Subduing guerillas without resorting to mass murder is where problems begin.