The Fourth in Christian Cameron's Long War series, The Great King has its protagonist, Arimnestos of Plataea return from his trips abroad as pirate and trader and returns to key events in the Persian War, including the buildup to the battle at Thermopylae and it's immediate aftermath and a in depth look at the naval battle at Artemisium (which has been covered far less often in popular culture).
The first half of the book focuses on the Olympic games of 484 BC, wherein Arimnestos witnesses just how close to fracture the Athenian and Spartan factions are in the face of the Persian empire, and the second half of the book begins with with a trip to the court of King Xerxes which looks like a trap even in the planning phase, and then the naval battle at Artemisium.
Much of what I've loved about the series continues here, with Cameron building his protagonist into a leader and father (sorry for the mild spoiler), rather than simply warrior, and a closer look at exactly how embassies and naval battles worked. The mission to Xerxes is in response to the Spartans killing his envoy (the whole "THIS IS SPARTA!" bit from 300) as you couldn't actually kill political envoys without having to send envoys of your own in response/apology.
Although not as complete a story as the previous three books (it definitely leads directly into the fifth book of the series, Salamis), The Great King is an engrossing look at the war from the ground level and definitely has me interested in completing the series.
1 month ago