Audio book. Sands of Time Book V, Time Runner Act 2: Antebellum.
 
How do you defend the entire world without them ever actually knowing they are in danger?
Dr. Theodore Ted Humphrey now  must do exactly that! Upon his return to Earth, with only the help of his companion EMMA. a sixth dimensional entity from outside this universe, sworn to never directly interfere with the  destiny of mankind, he must navigate the labyrinthian world and politics of the US shadow government, THE GROUP, the bloodline driven SUPREME COUNCIL and all the people that now work directly for him in the newly formed MRC-Maryland Research Council.

An unstoppable fleet advances towards Earth with the goal of  replacing the global population with their own. Somehow, in some mysterious way, this all relates to the three civilizations: ancient Babylonians, the Roman Empire and the Third Reich. And  Ted must solve the riddle of what and who connects them all, and how to defeat an implacable and impossible foe in the limited time he has left before they arrive in force to destroy and reclaim a planet they once claimed as their own and ruled with an iron fist!