The last book relates the consequences of the Athenian reply to Alexander. Mardonius advanced rapidly to Athens, which he captured a second time. The Spartans were busy keeping the feast of Hyacinthia; only an Athenian threat to come to terms with the foe prevailed on them to move. Mardonius soon evacuated Attica, the ground being too stony for cavalry, and encamped near Plataea. The Greeks followed, taking the high ground on Mount Cithaeron. A brave exploit of the Athenian infantry in defeating cavalry heartened the whole army. After eleven days' inaction, Mardonius determined to attack, news of his plan being brought secretly at night to the Athenians by Alexander. The Spartans, afraid of facing the Persians, exchanged places with the Athenians; when this movement was discovered by Mardonius, he sent a challenge to the Spartans to decide the battle by a single conflict between them and his Persian division. Receiving no reply, he let his cavalry loose on the Greeks who began to retire to a place called the Island, where horse could not operate. This action took place during the night. When morning broke the battle began. The Persian wicker shields could not resist their enemies' weapons; the host fled and after Mardonius fell was slaughtered in heaps. The Greek took vengeance on the Thebans who had acted with the Persians, of whom a mere remnant reached Asia under the command of Artabazus. The victorious Greek fleet had advanced as far as Delos, commanded by Leotychides, a Spartan of royal blood. To them came an embassy from Samos, urging an attack on the Persians encamped on Mycale. It is said that the battle was fought on the same day as that of Plataea and that a divine rumour ran through the Greek army that their brothers had gained the day. In the action at Mycale the Athenians took the palm of valour, bursting the enemy's line and storming his entrenchments. This victory freed Ionia; it remained only to open the Dardanelles. The Spartans returned home, but the Athenians crossed from Abydos in Asia to Sestos, the strongest fortress in the district. The place was starved into surrender; with its capture ends the story of Persia's attempt to destroy European civilisation.