From page 6 of the supplement:
Tomorrow you will bring the battle to the foe. Tonight you walk among the troops you’ll lead. The mercenaries are veterans and sleep while they can, but the anxious peasants levied from your lands seek comfort in recounting your victories. You sit at their campfire, wearing your ring of invisibility so that you can listen instead of command. Remember when you were like them? Back when you first entered the dungeon, you wielded a sword and fought for gold, glory, and the favor of the gods. Winning these earned you a throne. Now you wield an army, and fight for the right to rule the domains at war.
Domains at War (D@W) is a supplement for the Adventure Conqueror King System™ (ACKS) as well as two wargames in its own right - one for strategic campaigns, another for tactical battles. This Free Starter Edition focuses on the basics your fantasy RPG characters need to raise armies, conquer domains, and fight pitched battles. It also serves as an introduction to the Complete Domains at War Set which includes D@W: Campaigns and D@W: Battles, plus maps and counters for playing conflicts in more detail. The Complete Set is available separately from Autarch, but you don’t need it to enjoy the following rules. References to D@W: Campaigns and D@W: Battles are provided to help those who are using the Starter Edition to learn the Complete rules.