Cyrus was the son of Cambyses, ruler of Persia. His mother was the daughter of Astyages, ruler of Media, and so Cyrus links the ruling families of the Medes and Persians. Astyages ordered Harpagus to murder the infant Cyrus, but Harpagus did not carry out the order. Instead, Cyrus was raised as a peasant. When Cyrus reemerged, he began a campaign to take control of Astyages's kingdom. He was aided by Harpagus, who had been punished cruelly by Astyages for disobeying his command. Cyrus rallied the Persians to attack and conquer the Medes, overthrowing Astyages and adding the latter to a new Persian Empire. Cyrus then embarked on a career of expansion. He conquered Lydia and its famous king, Croesus. He then led the conquest of Babylonia and engaged in wars against the nomadic Massagetae. Cyrus met his death on this latter campaign.
Darius was the son of a governor. He had a lowly upbringing. He rose to power after deposing a conspiracy led by the magi, or priests, who had placed an impostor on the throne. Darius was then proclaimed king of Persia after a debate about the best form of government. Darius ruled the Persian Empire at its height. He reorganized the structure of the empire into 20 satrapies (provinces) and began infrastructure projects. He conquered Samos and put down a rebellion in Babylon. He also led massive armies on campaigns to conquer Libya and Scythia. The first was a partial success, the second a failure. While expanding into Macedonia, Darius conceived of a plan to invade Greece. This invasion was defeated by an Athenian-led army at the Battle of Marathon. A few years after this setback, while plotting revenge, Darius died.
Xerxes, son of Darius, inherited his father's empire. He had ambitions to exceed the deeds and conquests of his ancestors. He began with Egypt and then laid plans to invade Greece. He ordered the creation of the greatest army ever seen, devoting several years to his preparations. Xerxes's expedition against the Greeks proceeded with few initial setbacks. He was thwarted for two days at the Battle of Thermopylae, suffering great losses despite only facing a few thousand Greeks. Subsequently, Xerxes attacked and burned Athens, destroying the city's shrines. Xerxes's great invasion was halted by the Greek naval victory at the Battle of Salamis. Themistocles's fleet dealt the Persians a crushing blow by depriving them of the fleet they needed to support their great army. Xerxes's ambitions subsequently ended in disaster, and he was forced to retreat from Greece, never to return. The remnant of the Persian army was eventually defeated at the Battle of Plataea.
Themistocles was an intelligent and ambitious Athenian statesman. After becoming archon, or a ruling council member, he ordered the creation of the Athenian port at Piraeus and an expansion of the Athenian fleet. The fleet was meant to be used to fight the Athenian rivals on the island of Aegina, but was really intended to fight the Persians. Themistocles's confidence in Athenian naval power led him to order the city itself to be abandoned to the Persians. The Persians sacked the city, but Themistocles's navy was victorious at the Battle of Salamis. For his deeds, Themistocles was honored by the Spartans, after the other Greeks had tried to deprive him of the glory he was due.