Topic summary
Battle of Opis
Belshazzar
Gobryas
10,000 troops (other estimates)
The Battle of Opis was the last major military engagement between the Achaemenid Empire and the Neo-Babylonian Empire, which took place in September 539 BC, during the Persian invasion of Mesopotamia. At the time, Babylonia was the last major power in Western Asia that was not yet under Persian control. The battle was fought in or near the strategic riverside city of Opis, located north of the capital city of Babylon in modern-day Iraq, and resulted in a decisive victory for Persia. Shortly afterwards, the Babylonian city of Sippar surrendered to Persian forces, who then supposedly entered Babylon without facing any further resistance. The Persian king Cyrus the Great was subsequently proclaimed as the king of Babylonia and its subject territories, thus ending its independence and incorporating the entirety of the fallen Neo-Babylonian Empire into the greater Achaemenid Empire.