Darius III was the last king of the Achaemenid Empire, ruling from 336 to 330 BCE. He faced significant challenges during his reign, including internal strife and external threats, particularly from the rising power of Alexander the Great. Darius was known for his attempts to maintain control over his vast empire, which stretched from Egypt to parts of India. His reign ended after a series of defeats against Alexander, culminating in the decisive Battle of Gaugamela in 331 BCE. Following his defeat, Darius fled but was eventually captured and killed by his own satraps. His death marked the end of the Achaemenid Empire and the rise of Hellenistic influence in the region.