These units cost fewer initial resources, but require more upkeep, so they're good if you're caught unprepared when an enemy horde threatens a city - just hire some mercs and dismiss them from service once the threat has been defeated. Combat W3DLR has no user-controlled combat. Your stack and the enemy's fight to the death one unit at a time. Here, you have an isometric map on which to maneuver your forces, much like Warcraft and other real-time games. You can use items such as potions and spells as the battle progresses, and can pause at any time to evaluate your options.
Heroes are present on the battlefield like any other unit.
You can choose to autocalc a battle, either before it begins or at any point during it, which will immediately resolve the combat and determine losses. HOMM3 also has a separate combat mode, but it's turn-based on a hex map. Units move in order of speed, though you may have any unit delay its actions until after the others have moved. Unit values are affected by hero skills and artifacts, and certain ones allow you to redeploy your troops to different hexes before battle begins. When a unit is attacked hand-to hand, it automatically counterattacks once casualties have been removed, but most can only do this once per turn so that the effects of overwhelming assaults are represented.