[5][6] Charles de Flahaut volunteered for military service joining the cavalry in 1800, and received his army commission after the Battle of Marengo.

[4] After the Battle of Wagram, general Louis-Alexandre Berthier made him his Aide-de-camp, leaving the staff of Murat, and awarded him the empty title of Baron of the Empire.

[13] Flahaut was assiduous in his attendance on Queen Hortense de Beauharnais until the Hundred Days brought him back into active service.

[4] With the return of Napoleon from the island of Elba, Flahaut joined his campaign to Paris and was placed in charge of reforming the army to the Emperor's standard.

[4] Subsequently, he was attached to the household of Ferdinand-Philippe of France, Duke of Orléans and, in 1841, was posted as Ambassador to Vienna, where he remained until 1848, when he was dismissed and retired from army service.

After the Coup d'état of 1851 by Napoleon III, his services were re-engaged, and from 1860 to 1862 he served in Britain as French Ambassador to the Court of St James's under Queen Victoria.

[16] In 1864, the Flahauts returned to Paris and took up residence at the Hôtel de Salm, when Charles was appointed Grand Chancellor of the Legion of Honour.