The objective in Days of Ruin is for the player to use their military force to defeat the enemys force. Except for certain single player missions with special objectives there are two ways to defeat an opponent destroy all of the enemys units or capture their headquarters. The battle system is turn-based. Two to four forces each headed by a commanding officer (CO) take turns building and commanding units on grid-based maps. Every turn units which consist of ground sea and air units can move across the different types of terrain and attack enemy units or perform other actions such as submerging a submarine or resupplying friendly units. Many factors can affect the battle such as Fog of War a phenomenon that prevents players from seeing enemy units other than those in the visual range of their units various weather conditions and CO powers