This is what total war looks like. Make continuing the war so costly to the population that the other side gives up and won’t try again for generations.
This is the modern day equivalent to Sherman’s march to the sea in Georgia.
It's especially important to get all the children, women and elderly people who have literally zero influence on anything and to then extinguish the entire basis for their livelihoods wholesale. In fact, they're the easiest to punish for whatever someone else has done or is doing or will do -doesn't matter, excuses will be made up- because they can't defend themselves when you take everything they own. Galaxy brain material here, truly.