The sling is a common missile weapon used for hunting. They are long range and hard hitting even more so when lead bullets are used. A wicker shield that might stop an arrow from a common bow might not stop a sling bullet, though they are also very hard to master. As such families which can produced skilled slingers are worth more than the usual collection of levies. Some cities incentivise slingers by offering them extra rations on campaign, holding sling competition and exempting those who have the skill from corvee labor. Since kids that have parents showing them the ropes tend to have a higher success rate than those that try to master it on their own, gradually sling skirmishers grow into a hereditary class mostly drawn from herders in the more pastoral provinces of the Kingdom which can get better armor than the common spear levies.