In this universe, the point of divergence occurs when the Prophet Muhammad (Mouamet), instead of developing Islam, converted to Christianity and became a celebrated prelate and saint.

The Emperor Constans II subdued the Lombards in Italy, and the Iberian Peninsula (Ispania) and the southern coast of Gaul were also recovered.

In the East, the Byzantines are still—as it was in our history up to the advent of Islam—involved in a never-ending cold war (occasionally flaring up into actual fighting) with its arch-enemy, the Sassanid Empire, represented in the series by the female spy Mirrane.

Argyros works as an army scout, and later as a magistrianos for the Master of Offices, under the (fictional) Emperor Nikephoros III, and as such is sent across the Empire to solve problems—sometimes as a spy, sometimes as a negotiator, and sometimes as a soldier.

Orson Scott Card praised Turtledove as "a very talented science fiction writer, with a gift for finding a way to present a fascinating idea through strong, believable characters.