How do I activate first person view during a battle?

To activate first person view during a battle, select a unit and press the "\" key.

You will then see the battle from the perspective of the selected unit.

To return to an overhead view, press the "\" key again.

NOTE: If you have remapped your controls, the required key may be different from that listed above. You can view and edit your current control configuration in the Controls menu (Main Menu → Options → Controls). The command to activate first person view is listed as Context camera under the Universal tab.