Historical imagery
The novel is historical fiction, so it blends historical fact and well-known stories with a tangible narrative that is invented. This turns historical knowledge into imagery. This adds depth and dramatic irony to the story, because although the reader knows facts about the story, they have to see the story unfold dramatically through the eyes of Xerxes, who learns about the battle through real-time updates from his messenger.
Thermopylae and the pass
The imagery of the battle is shaped by the natural terrain. The imagery of nature becomes extremely pertinent when the Greeks exploit a natural advantage, luring the Persians into a narrow pass where they are surprised to meet the Spartan elite. See, on an open battlefield, the imagery would give an advantage to the Persians, for sheer number, but in this narrow pass, their numbers don't have access to overwhelm the Greeks the way they otherwise might. The Spartans are able to defeat the Persians easily, because the funnel slows their approach; they fight one-on-one.
Battle and death
The war involves an obvious use of battle imagery. The battle is a machine that produces death tolls. Throughout the work, death is viewed in two ways: statistically and personally. When Xerxes's officers fall, that means a different thing than the deaths of soldiers he doesn't know. The dynamic shows that battle has a way of distancing the leadership from the real horror of death. For Xerxes, this is a good thing, but for the people on the battlefield, the imagery would be absolutely horrific and quite dangerous. To Xerxes, the imagery of battle is reduced to a game of chess. He is playing a strategy game with real human pieces.
Authority and administration
The shape of Xerxes's authority and administration is an important imagery to notice, because before this era of human life, the nation of Greece was not unified; it is the rise of great empires that force tribal communities to cooperate. From the Persian side of the story, the reader sees the administration at work. Xerxes communicates with leaders who rule over small factions of soldiers in a tree of authority; he is away from the battle, preserving the authority of his role by not risking his own life. He communicates with the battle through a messenger who gives him updates.
