Over a 10-year period, fighting across modern-day Turkey, the Middle East, and as far away as Afghanistan and Pakistan, Alexander routed Persian king Darius III, taking the empire for his own.

Darius I (548-486 BC) assumed the throne of Persia ... it. Under Darius’s rule, Zoroastrianism became the state religion, providing a cohesive sense of identity across his far-flung empire.