This miniature portrait is signed by an artist named Berteaux. This does not appear to be the name of an acknowledged miniature artist, so the portrait is more of a cross-over type between a "genuine" miniature and a "decorative" one. The quality puts it out of the normal range for a decorative miniature.
The sitter is Eugène Rose de Beauharnais, Prince Français, Prince of Venice, Viceroy of the Kingdom of Italy, Hereditary Grand Duke of Frankfurt, 1st Duke of Leuchtenberg and 1st Prince of Eichstätt ad personam (3 September 1781 – 21 February 1824). He was the first child and only son of Alexandre, Vicomte de Beauharnais and Joséphine Tascher de la Pagerie, future wife of French Emperor Napoléon I. His natural father was executed during the revolutionary Reign of Terror. For a miniature portrait of his father, which is in this collection, see View
Eugene was born in Paris, France and became the stepson and adopted child (but not the heir to the imperial throne) of Napoleon. He commanded the Army of Italy and was viceroy of Italy under his stepfather. Historians have looked upon him as one of the ablest of Napoleon's relatives.
Although there are obvious differences, it appears the miniature was inspired by the same original as was a portrait of Eugene in uniform by the famous artist Jachues-Louis David. Another version, in similar pose but wearing a black cloak dates from 1837. So far I have not located an original version depicting the same green uniform as appears above. However, it is probable that the "missing" original wearing a green uniform pre-dates the black uniform in the David portrait, as Eugene appears to be of higher rank and is wearing more decorations in the David portrait.
According to Wikipedia, Eugène's first campaign was in the Vendée, where he fought at Quiberon. However, within a year his mother Joséphine had arranged his return to Paris. In the Italian campaigns of 1796–1797, Eugène served as aide-de-camp to his stepfather, whom he also accompanied to Egypt. In Egypt, Eugène was wounded during the Siege of Acre (1799). He returned to France in the autumn of 1799 and helped bring about the reconciliation which then took place between Bonaparte and his mother, torn apart by each other's affairs. When Napoleon became First Consul, Eugène became a captain in the Chasseurs à Cheval of the Consular Guard and with his squadron he took part in the Battle of Marengo.
During the War of the Fifth Coalition, Eugène was put in command of the Army of Italy, with General Étienne-Jacques-Joseph-Alexandre MacDonald as his military advisor. In April 1809 he fought and lost the Battle of Sacile against the Austrian army of the Archduke John, but Eugène's troops decisively won the rematch at the Battle of Raab that June. After the Battle of Aspern-Essling, Napoleon recalled the Army of Italy and after joining the main army, on the island of Lobau in the Danube, Eugène took part in the Battle of Wagram.
During the Russian campaign, Eugène again commanded the Army of Italy (IV Corps) with which he fought in the Battle of Borodino and the Battle of Maloyaroslavets. After Napoleon and then Joachim Murat had left the retreating army, Eugène took command of the remnants and led it back to Germany in 1813.
During the campaign of 1813, Eugène fought in the Battle of Lützen. Napoleon then sent him back to Italy, where he organised the defence against the Austrians, holding out on the Mincio until the abdication in 1814. After the fall of Napoleon in 1814, Eugène retired to Munich and at the behest of his father-in-law Maximilian I Joseph of Bavaria, did not get involved with Napoleon and France again. 1449