Ernest fought against Napoleon Bonaparte, and through construction projects and the establishment of a court theatre, he left a strong imprint on his residence town, Coburg.

On 10 May 1803, aged 19, Ernest was proclaimed an adult because his father had become gravely ill, and he was required to take part in the government of the duchy.

As the biographer Lytton Strachey put it: "The ducal court was not noted for the strictness of its morals; the Duke was a man of gallantry, and the Duchess followed her husband's example.

In Coburg on 23 December 1832, Ernest married his niece Duchess Marie of Württemberg, the daughter of his sister Antoinette.

[3]: 106 After the defeat of Napoleon in the Battle of Waterloo, the Congress of Vienna on 9 June 1815 gave Ernest an area of 450 square kilometres with 25,000 inhabitants around the town of St. Wendel.

However, he was at that time in the process of divorcing Louise, and the other branches used this as a leverage to drive a better bargain for themselves by insisting that he should not inherit Gotha.

[3]: 107  He is chiefly remembered for the economic, educational and constitutional development of his territories, and for the significant international position attained by the house of Coburg.

[1] Ernest died on 29 January 1844 and was initially buried in the Morizkirche but later reinterred in the newly built mausoleum in Friedhof am Glockenberg [de].