The Persian War began after the Persians conquered Lydia and placed tyrants to control the new Greek city-states. The Athenians helped the Lydians revolt but then withdrew, allowing Persia to regain control of Lydia. In 490 BCE, the Athenians met the vengeful Persians at Marathon and were outnumbered but used strategy to defeat the Persians. This victory prevented the destruction of Athens and allowed the Greek-Persian war to continue. The key battles after Marathon were Thermopylae, Salamis, and Plataea, culminating in the Greeks defeating the Persians at Plataea and ending the war.