539 BCE
28? – Battle of Opis: Troops of the Persian Achaemenid Empire under Cyrus the Great decisively defeat those of the Neo-Babylonian Empire. Fall of Babylon: Achaemenid troops under Gobryas enter Babylon unopposed. Cyrus enters the city, incorporating the Neo-Babylonian Empire into the Achaemenid Empire and turning the latter into the largest in the history of the world up until that point.
Conflict & Security
- September 25–28? – Battle of Opis: Troops of the Persian Achaemenid Empire under Cyrus the Great decisively defeat those of the Neo-Babylonian Empire.source
- October 29 – Fall of Babylon: Achaemenid troops under Gobryas enter Babylon unopposed. Cyrus enters the city, incorporating the Neo-Babylonian Empire into the Achaemenid Empire and turning the latter into the largest in the history of the world up until that point.source