We begin with the cataclysms, both local and systemic, that set Rome on a wholly new course. Between about 410, when Alaric’s Goths became the first non-Roman army to capture and pillage Rome in 800 years, and the middle of the 6th century, when Byzantine and Gothic armies pulled the city apart in a murderous tug-of-war lasting almost two decades, the urban population declined by a full order of magnitude, from over a half-million to something like 50,000. A millennium would pass before the latter figure was again exceeded. Even at the height of Italy’s communal age in the 13th century, when the mercantile and banking centers of Milan and Florence boasted 100,000 residents or more, Rome had maybe 50,000, a number equaled or exceeded also by Venice, Genoa, Bologna, Pisa, Siena, and Palermo.