Battle of Opis

Final battle between the Neo-Babylonian Empire and the Achaemenid Empire

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.

This keyword could refer to multiple things. Here are some suggestions: