Zone of Control is a concept in Nectaris and Game Boy Wars 3. It is not used in any of the Nintendo Wars series except Game Boy Wars 3.
The Zone of Control is the area of spaces adjacent to each unit. Each unit grants its army some control over those spaces, in addition to the full control of the spaces the unit is on. There are two important traits of ZoC: movement restricton and encirclement.
Because of the Zone of Control's power, a unit may not move onto a space adjacent to an enemy unit and then onto any other space at all in a single Movement command. (Note that it's a single Movement command; this will not stop the ability to move directly after firing.) In Game Boy Wars 3, the Attacker S and Mercenary Bomber ignore this restriction, but are still unable to move directly onto or through spaces with enemy units, and they are still susceptible to the effects of Encirclement.