The Falcon of Sparta by Conn Igguldon (2019)
More than 100 years before Alexander, Greek mercenaries from Athens and Sparta join Cyrus, younger brother to the Persian ruler Artaxerxes in an attempt to gain Cyrus' rightful place in the Kingdom. Events do not go well for Cyrus nor the mercenaries and they are left with only Xenophon, a young Greek officer to lead them away from the Persian hordes seeking their destruction. Xenophon reminisces about his earlier conversations with Socrates as he leads the remnants of his army out of reach of the Persians and into the mountains controlled by savage tribes. During their flight, both the Persians and mountain tribes gain great respect for the skill and ferocity of the Spartan warriors.