Babylon's Ashes is the sixth book in The Expanse series by James S. A. Corey. It was published on December 6, 2016.
The title of the book refers to the fall of the Babylonian Empire, which occurred after a long and brutal war with the Persians. The Persian king Cyrus the Great conquered Babylon in 539 BC, and ended the empire's rule over Mesopotamia. The event was a turning point in world history, as it marked the end of one of the most powerful empires of antiquity and ushered in a new era dominated by Persia.
The title also references ashes to ashes, dust to dust, which is a phrase often used in funerals to symbolize the finality of death. In this case, it reflects both the destruction of Babylon and its people, as well as their eventual demise (the city was eventually abandoned and forgotten).