Thus, during their childhood and adolescence, he and his elder brother, Prince Philippe, Count of Paris, were mainly looked after by their grandparents, King Louis-Philippe and Queen Marie-Amélie.

During the French Revolution of 1848, King Louis-Philippe refused to fire upon the revolutionaries, instead abdicating his throne in favour of his grandson Philippe on February 24.

Helene and her children then left France for Germany, whilst King Louis-Philippe and the rest of the royal family moved to the United Kingdom.

Sent to Turin for military training shortly after his mother's death, the Duke of Chartres became an officer in the Piedmontese dragoons and fought in the Wars of Italian Unification on the side of France and the House of Savoy from 1859 onwards.

With the outbreak of the American Civil War in April 1861, Chartres and his brother, Prince Philippe, Count of Paris, travelled to the United States to support the Union cause.

Although eligible for membership, Chartres did not join (as his brother had) the Military Order of the Loyal Legion of the United States – an organization of Union officers who had served during the American Civil War.