For almost 18 years, Louis-Alexandre Berthier followed Napoleon in all his campaigns, transcribing and transmitting his orders with fidelity. Although Napoleon rewarded him with honors and riches, ultimately Berthier was undervalued. Widely seen as colorless and lacking in spirit, falsely accused of treason in 1814, dead under mysterious circumstances in 1815, Berthier remains underappreciated. This study reveals the complexity of Berthier's character and history: his role in the armies of Louis XVI, his part in the American Revolution, his passionate love for an Italian marquise, his marriage to a Bavarian princess, his administration of a landed estate without equal in imperial France.