Click here for the link to the site's podcast companion!
In the world of Avatar, some people in each of the four nation are Benders. Benders are people with the ability to manipulate their native element. Not everyone in the four nations are benders.
Water Tribes: 20% population are benders.
Earth Kingdom: 20-25% population are benders.
Fire Nation: 35-40% population are benders.
Air Nomads (pre-genocide) : 100% population are benders.
This means that the rest of them are non-benders. If they wanted to join their Nation's Military, they would have to wield weapons.
This chart shows the different bending forms and the sub-bending forms which derive from them.