It was afterwards asserted that, on Napoleon's resolve to turn the army of England against Austria, Daru had set down at the emperor's dictation all the details of the campaign which culminated at Ulm.
After the first abdication of Napoleon in 1814, Daru retired into private life, but aided Napoleon during the Hundred Days.
He shares with Daru the honour of being the hardest worker and most devoted supporter in Napoleon's service; but it has generally been considered that he carried devotion to the length of servility, and thus often compromised the real interests of France.
The accession of Napoleon Bonaparte to power in November 1 799 led to the employment of Daru as chief commissary to the Army of Reserve intended for North Italy, and commanded nominally by Berthier, but really by the First Consul.
At the congress of Erfurt, Daru had the privilege of being present at the interview between Goethe and Napoleon, and interposed tactful references to the works of the great poet.