section_path: History/Formation and expansion/510s BC
section_name: 510s BC
paragraph_text: 510s BC
  
  Ever since the Macedonian king Amyntas I surrendered his country to the Persians in about 512–511, Macedonians and Persians were strangers no more as well. The subjugation of Macedonia was part of Persian military operations initiated by Darius the Great (521–486) in 513—after immense preparations—a huge Achaemenid army invaded the Balkans and tried to defeat the European Scythians roaming to the north of the Danube river. Darius' army subjugated several Thracian people, and virtually all other regions that touch the European part of the Black Sea, such as parts of modern Bulgaria, Romania, Ukraine, and Russia, before it returned to Asia Minor. Darius left in Europe one of his commanders named Megabazus whose task was to accomplish conquests in the Balkans. The Persian troops subjugated gold-rich Thrace, the coastal Greek cities, and defeated and conquered the powerful Paeonians. Finally, Megabazus sent envoys to Amyntas, demanding acceptance of Persian domination, which the Macedonians did. The Balkans provided many soldiers for the multi-ethnic Achaemenid army. Many of the Macedonian and Persian elite intermarried, such as the Persian official Bubares who married Amyntas' daughter, Gygaea. Family ties that the Macedonian rulers Amyntas and Alexander enjoyed with Bubares ensured them good relations with the Persian kings Darius and Xerxes I, who was also known as Xerxes the Great. The Persian invasion led indirectly to Macedonia's rise in power and Persia had some common interests in the Balkans; with Persian aid, the Macedonians stood to gain much at the expense of some Balkan tribes such as the Paeonians and Greeks. All in all, the Macedonians were "willing and useful Persian allies. Macedonian soldiers fought against Athens and Sparta in Xerxes I's army. The Persians referred to both Greeks and Macedonians as Yauna (" Ionians ", their term for "Greeks"), and to Macedonians specifically as Yaunã Takabara or "Greeks with hats that look like shields", possibly referring to the Macedonian kausia hat.