The different types of units available to the defender encourage a combined-arms approach with each type being better than the others in different aspects. Heavy tanks have high attack and defense with moderate speed and low range. Missile tanks have moderate attack and defense with moderate range and low speed. G.E.V.s ("ground effect vehicles"—roughly, heavily armored hovercraft) have very high speed (moving twice per turn), low attack, low range, and moderate defense. Howitzers have very high attack and range but are easily destroyed (once an attacker has managed to get close enough), immobile, and expensive. However, according to the game's designer, this balanced mix of units was not quite right in the first edition; the second edition sped up heavy tanks, slowed down G.E.V.s, and changed the defender's purchasing from "attack factors" to "armor units" (everything is considered equivalent, except howitzers, which are worth two of anything else).
