On October 1, 331 BCE at the plain of Gaugamela (near Mosul), Alexander's 47,000-strong army defeated Darius III's larger force. Darius fled the battlefield, and the 228-year-old Achaemenid Empire collapsed.
Fun Facts
Darius III flattened the ground before battle to make his scythed chariots more effective, but Alexander's tactics neutralized this plan. Bessus, satrap of Bactria, later killed Darius. Alexander found him and executed him in Persian fashion—showing respect for the defeated king.
Related Events
Foundation of Achaemenid Empire
Cyrus II (Cyrus the Great) rebelled against Astyages, the Median king and his maternal grandfather, winning the Battle of Pasargadae (550 BCE). Uniting Persians and Medes, he founded the Achaemenid Empire—history's largest empire to that date, spanning from the Indus to the Aegean.
Fall of Babylon to Persian Army
On the 16th of Tishri (around 15-20 Mehr), Persian forces under Gobryas (Ugbaru) entered Babylon without battle. Nabonidus, the last Babylonian king, fled, and the city surrendered peacefully. This peaceful conquest marked a turning point in world history.
Cyrus the Great Day (Entry into Babylon)
According to the Nabonidus Chronicle, on the 3rd of Arahsamnu (7 Aban), Cyrus the Great personally entered Babylon, 17 days after the city fell to Persian forces. The chronicle states: 'Green branches were spread before him' and the people welcomed him magnificently. Cyrus sent greetings of peace and friendship to all cities.
Conquest of Egypt by Cambyses II
Cambyses II defeated Pharaoh Psamtik III at the Battle of Pelusium, making Egypt the 27th Achaemenid satrapy. He adopted the title of Pharaoh and took the Egyptian name "Mesuti-Ra" (Born of Ra).