well as the re-subjugation of Thrace and the conquering of Macedonia in 492 BCE under Mardonius. Macedon had been a vassal kingdom of the Persians since the late 6th century BC, but retained autonomy. Mardonius' 492 campaign made it a fully subordinate part of the Persian kingdom. These military actions, coming as a direct response to the revolt in Ionia, were the beginning of the First Persian invasion of (mainland) Greece. At the same time, anti-Persian parties gained more power in Athens, and pro-Persian aristocrats were exiled from Athens and Sparta. Darius responded by sending troops led by his son-in-law across the Hellespont. However, a violent storm and harassment by the Thracians forced the troops to return to Persia. Seeking revenge on Athens and Eretria, Darius assembled another army of 20,000 men under his Admiral, Datis, and his nephew Artaphernes, who met success when they captured Eretria and advanced to Marathon. In 490 BCE, at the Battle of Marathon, the Persian army was defeated by a heavily armed Athenian army, with 9,000 men who were supported by 600 Plataeans and 10,000 lightly armed soldiers led by Miltiades. The defeat at Marathon marked the end of the first Persian invasion of Greece. Darius began preparations for a second force which he would command, instead of his generals; however, before the preparations were complete, Darius died, thus leaving the task to his son Xerxes. Family Darius was the son of Hystaspes and the grandson of Arsames. Darius married Atossa, daughter of Cyrus, with whom he had four sons: Xerxes, Achaemenes, Masistes and Hystaspes. He also married Artystone, another daughter of Cyrus, with whom he had two sons, Arsames and Gobryas. Darius married Parmys, the daughter of Bardiya, with whom he had a son, Ariomardus. Furthermore, Darius married Phratagune, with whom he had two sons, Abrokomas and Hyperantes. He also married another woman of the nobility, Phaidyme, the daughter of Otanes. It is unknown if he had any children with her. Before these royal marriages, Darius had married an unknown daughter of his good friend and lance carrier Gobryas from an early marriage, with whom he had three sons, Artobazanes, Ariabignes and Arsamenes. Any daughters he had with her are not known. Although Artobazanes was Darius's first-born, Xerxes became heir and the next king through the influence of Atossa; she had great authority in the kingdom as Darius loved her the most of