After losing the Siege of Mainz (1793) he was imprisoned and executed by guillotine on 23 July 1794, a few days before the fall of Maximilien Robespierre and the end of the Reign of Terror.

[2] Eugène joined the French Revolutionary Army soon after his father's death, initially serving as an orderly to General Lazare Hoche during the War in the Vendée.

[4] After joining the 1st Hussar Regiment as an assistant sub-lieutenant on 30 June 1797, Eugène served as an aide-de-camp to his stepfather in the Italian campaign.

[4] Eugène returned to France with Napoleon in the autumn of 1799, helping to bring about the reconciliation of the general and his mother, who had become estranged due to their mutual extramarital affairs.

When Napoleon became First Consul following the coup, Eugène was appointed captain of the chasseurs à cheval of the Consular Guard.

During the coronation, Napoleon handed the royal ring and mantle to his stepson and on 7 June 1805 announced Eugène's appointment as Viceroy of Italy to the Italian Legislative Assembly.

[4] Though excluded from succession to the French Empire, on 16 February 1806 he was declared heir presumptive to the Italian throne, in the absence of a second son of Napoleon.

[4] During the War of the Fifth Coalition, Eugène was put in command of the Army of Italy with some highly competent generals like Grenier, Charpentier, and the future marshal Étienne MacDonald accompanying him as advisers and officers.

[7] After joining the main army on the island of Lobau in the Danube, Eugène took part in the Battle of Wagram.

[3] After Napoleon and then Joachim Murat had left the retreating army in December 1812, Eugène took command of the remnants of the Grande Armée at Poznań.

[4] On 16 April, five days after Napoleon's abdication of both the French and Italian thrones, Eugène signed the Convention of Schiarino-Rizzino [it] with the Austrian commander Heinrich von Bellegarde, bringing an end to hostilities.

[4] As Duke of Leuchtenberg, Eugène lived his last years in Munich managing his estates and expanding his art collection.

At the same time, he provided assistance for proscripts under the Bourbon Restoration, such as Antoine Marie Chamans de Lavalette, and lobbied for the alleviation of the harsh treatment imposed on Napoleon in his captivity in Saint-Helena.