Who was Napoleon Bonaparte's chief of staff throughout nearly all his European military campaigns?

Louis-Alexandre Berthier (1753-1815), was a Marshal of the Empire doubling as Minister of War and brilliant chief of staff to French emperor Napoleon Bonaparte during his military campaigns stretching from 1796 to 1814. His power of work, accuracy and quick comprehension, combined with his long and varied experience and his complete mastery of detail, made Berthier the ideal chief of staff. In this capacity, Berthier was Napoleon's most valued assistant for the rest of his career. His reputation as a superb organizer remains strong among current historians.

Berthier was an aggressive and imaginative officer, whose character shone in victory and defeat, triumph and adversity. He could rally a broken column of infantry, seize a regimental color and lead it forth in combat, as he did at Lodi in 1796; or, in what probably was the most important action he ever completed, pulling the wreck of the Grande Armee together in Poland at the end of the disastrous Russian campaign.

Napoleon summed up Berthier's overall worth as a soldier; and to the Grande Armee in general, referring to his absence at Waterloo, "If Berthier had been there, I would not have met this misfortune."

Before Napoleon met his defeat at Waterloo, Marshal Berthier had retired to Bamberg, Germany, where on June 1, 1815, he fell to his death while supposedly leaning too far from a third-storey window.