Ah but they would also have no compunction against the use of chemical agents.
One of the advantages of a country with regular rainfall is that it really mitigates chemical attacks.
Makes them harder to deliver and very much less effective. And airborne delivery is very tricky in locations like the Scottish Highlands, you need to be low enough for effective delivery on a day when it's clear enough so you don't fly into a mountain, but high enough you don't fall victim to man carried AA weapons.
You could probably get some insight by looking at anti-guerilla operations in Crete during WW2, or Cyprus post-WW2. Neither went particularly well for the anti-guerilla forces.