From the PDF introduction
Battlefield Encounters for 4th-, 8th-, and 10th-Level Player Characters Featuring Material from Heroes of Battle
Heroes of Battle brings the dungeon out onto the battlefield and enables Dungeon Masters (DMs) to set adventures against the backdrop of armed conflict. Whether player characters (PCs) lead army units into battle or perform elite missions on behalf of battle leaders, the foes they face on the battlefield are just as lethal as any they would find in a dungeon. In addition to new battle-oriented spells, feats, and items, Heroes of Battle presents plenty of sample battlefield encounters that can be dropped into any war-based scenario.
Theaters of Death is a collection of new battlefield encounters (for characters from 4th to 10th level) are designed to supplement those pre s e nted in Chapter 3 of Heroes of Battle. These scenarios are nonlinear and not designed to work with any one specific battle. Thus, each can be dropped into a mass combat of your choice, or modified to work with a variety of different battles. Like the battlefield encounters given in Heroes of Battle, these scenarios can easily be reused simply by changing the specific creatures or terrain. As always, feel free to adapt the material presented here as you see fit to make it work with your campaign.
Theaters of Death is not set in a specific campaign world. In fact, in most cases, no specific names or places are given, so that you can more easily drop the encounter into your campaign.