There are four types of combat: ground/naval combat, bombardment, missile attacks, and air combat. Ground/Naval combat occurs when units of different civilizations try to occupy the same square. The two units trade blows until one of them loses its health bar and is destroyed. The winner may be damaged (its health bar is reduced). Bombardment occurs when a ranged unit or air unit attacks without entering the defender's square. Bombardment inflicts losses to the defender's health bar but never completely destroys them. Air bombardment is the same except the planes fly to the target and may be shot down on the way. Missile attacks are like bombardment, but the unit never returns to its base and the attacks can destroy enemy units. Air combat occurs between air units. Repairing Damage A unit that takes damage in combat but survives can heal, adding one block per turn back to its health bar. To do so, it * must be in friendly or neutral territory. * must not move for a complete turn. Repairing Faster A city with a barracks heals ground units completely in one turn. A city with a harbor heals sea units completely in one turn. A city with an airport heals air units completely in one turn. A civilization with Battlefield Medicine heals in enemy territory.