Stop sending food into the cities. Pick off the armies that come out to the farms to commandeer the food production and distribution network. Burn the crops, blow up storage, and retreat with all the farming equipment and tools in a deep defense strategy away from the coasts and towards the Mississippi. They will have to deal with attrition while trying to hold and replant farmland. They can only afford 1 assault. Country boys just need enough ammo and know how to wait until the cities revolt against their new commie rulers then offer a magnanimous peace.