Battle screen

By default, battles are automated turn based events. Units nominally act in order of their speed, scaled by the hero speed.

Melee units advance towards the "most threatening" enemy stack at the start of their turn and attack if they are in range at the end. Typically this means the stack with the highest summed attack within the closest general range (middle of battlefield is normal)

Ranged units fire on the "strongest" enemy stack at the start of their turn.

This continues until one side loses all its units or time runs out.

You can give general advance/stand/retreat commands via the lower left buttons, and to specific units by clicking on them or their portrait. Use this to your advantage to get first attacks and have your ranged take out their ranged first if appropriate.

You can also cast spells, provided they have been researched (mage tower) and equipped (hero tower).

Losing units: when you lose units in combat, about 75% are immediately transfered to your castle's arena -> infirmary as injured. The other 25% are permanently lost. You can get the injured units back via the Barracks/Graveyard->infirmary for a gold cost. Once healed the units are placed in your castle army. You have to re-allocate them to heroes.