Gates of fire tells the story of Xeones, a captive Greek from the city-state of Sparta. Through him, like a looking glass, we the readers can get a glimpse into the subtleties of everyday life in the ancient period in Greece. More specifically, the narrative helps the reader understand how the military in the broader Greek empire operated, protected and fought for its citizens, and what tactics they used to achieve their goals.

One thing the reader gets a sense of through Xeones narrative about his life in Sparta, is of the differing cultural and societal perceptions of patriotism between the modern and ancient west. Modern patriotism is much more nationalistic. This is no doubt due to the relatively recent invention of the concept of the nation-state, from which the identity attachments flowed. In the ancient period, however, patriotism, as we can see with Sparta and Athens, one's city-state and the surrounding region takes on much more of an importance and sense of meaning for one's identity. We see this play out with Xeones, who has no home and arrives in Sparta as a slave. Yet he choose Sparta to immigrate to, between Athens, who also accepted immigrants, and develops a strong sense of patriotism. At least enough to feel the need to fight passionately, with the very good possibility of death, for Sparta, to protect what he felt was his home.

Much of Pressfield's narrative explores Spartan military society, particularly the agoge, the rigid, extensive 13 year military education and training program Spartan youth were inundated in.