Herodotus, 8: The Battle of Salamis

Retreating after the eventual loss at Thermopylae, the Hellenes try to determine their next course.  The Spartans, Argives, and Achaians build a wall across the Isthmus of Corinth to protect Peloponnesia.  All the residents of Athens are evacuated to the island of Salamis.

The Persian army sacks Athens, while the Persian navy surrounds the island.  Xerxes is advised to simply wait them out, and victory will be his.  Meanwhile, the Hellenes cannot come to an agreement about what to do next.  So Themistokles from Athens secretly sends a messenger to Xerxes, pretending to have changed sides, and encouraging him to begin a final battle he is expected to win.  This message convinces Xerxes to abandon his strategy of patience, and his action then convinces the Hellenes to pull together to fight.

The battle is a massacre in favor of the Greeks, who have well-developed naval tactics while the Persian ships all act at odds with one another.

Xerxes, chastised, leaves an army of 300,000 with the commandor Mardnios and returns to Persia with the rest.  Many die of hunger and sickness on the way home.  At one point, Xerxes was in peril on a ship during a storm, and the helmsman through most of the Persian soldiers overboard to steady the ship.  Xerxes rewarded him with a crown for saving his life, then beheaded him for killing so many soldiers.  (Herodotus seriously doubts this story.)

Mardonios tries to buy off the Athenians without a fight.  They string him along for a bit, long enough for the Spartans, panicking, to send envoys to find out what's going on.  The Athenians calmly tell off the Persians, and tell off the Spartans for good measure (8.143):

The Athenians first answered Alexandros as follows: "We ourselves are already well aware that the forces of the Mede are many times greater than our own, so there is no need to admonish us about that.  Nevertheless, we shall defnd ourselves however we can in our devotion to freedom.  So do not attempt to seduce us into an agreement with the barbarian, since we shall not be persuaded.  Report back to Mardonios that the Athenians say: 'As long as the sun continues on the same course as it now travels, we shall never come to an agreement with Xerxes.  Trusting in the gods and heroes as our allies (for whom he showed no respect when he burned their homes and images), we shall advance against him and defend ourselves.'  As for you, Alexandros, in the future, do not appear before the Athenians with speeches such as this one, nor pretend to be doing us a favor while encouraging us to commit deeds that violate all tradition.  For we would not want you, our proxenos and friend, to suffer anything unpleasant at the hands of the Athenians.

After giving this answer to Alexandros, they turned to address the messengers from Sparta: 'It was quite natural for the Lacedaemonians to fear we would come to an agreement with the barbarian, but nevertheless, we think it disgraceful that you became so frightened, since you are well aware of the Athenians' disposition, namely, that there is no amount of gold anywhere on earth so great, nor any country that surpasses others so much in beauty and fertility, that we would accept it as reward for medizing and enslaving Hellas.'"

Notables: Artemisia was a female commander in Xerxes army.  At one point, her ship was pinned in by the surrounding Persian ships while pursued by a Greek ship.  To escape, she rammed a Persian ship, causing the pursuit to cease while Xerxes looked on, impressed.

8.98:

As Xerxes was doing all this, he also sent a courier to Persia to report his present misfortune.  There is nothing that travels faster, and yet is mortal, than these couriers; the Persians invented this system, which works as follows.  It is said that there are as many horses and men posted at intervals as there are days required for the entire journey, so that one horse and one man are assigned to each day.  And neither snow nor rain nor heat nor dark of night keeps them from completing their appointed course as swiftly as possible.  The first courier passes on the instructions to the second, the second to the third, and from there they are transmitted from one to another all the way through,  just as the torchbearing relay is celebrated by the Hellenes in honor of Hephaistos.  The Persians call this horse-posting system the angareion.

The Persians invented the Pony Express, and Herodotus wrote the U.S. Postal Service Creed.  Son of a bitch.