In 1803, the Imperial diet raised the Duchy of Württemberg to an Electorate, the highest form of a princedom in the Holy Roman Empire.

During the short reign of Frederick II Eugene, the French Republic invaded Württemberg and compelled the duke to withdraw his troops from the Imperial army and pay reparations.

He took part in the War of the Second Coalition against France in defiance of the wishes of his people and, when the French again invaded and devastated the country, he retired to Erlangen, where he remained until after the conclusion of the Treaty of Lunéville on 9 February 1801.

Following the German mediatisation with France, signed in March 1802, he ceded his possessions on the left bank of the Rhine, receiving in return nine free imperial cities, among them Reutlingen and Heilbronn and other territories, amounting altogether to about 850 square miles and containing about 124,000 inhabitants.

In 1805 Württemberg took up arms on the side of the First French Empire, and in the Peace of Pressburg in December 1805 the elector was rewarded with various parts of Further Austria in the Swabian Circle and with other lands in the area.