On 17 June 1805 Jean Baptiste Bernadotte was made Governor of Hanover, and on 29 August 1805 took control of the new I Corps, and remained in this role for another seven years.

During the famed Ulm campaign, the I Corps formed part of the far left flank, preventing the possible retreat of the Austrians under General Karl Mack von Leiberich.

After Bernadotte was wounded at Spanden, General Claude Victor-Perrin led the I Corps at Friedland where his tactics earned him a marshal's baton.

The corps was reorganised into a strength of five infantry divisions for the invasion of Russia in 1812 and Marshal Louis-Nicolas Davout was appointed to lead it.

[5] Under Davout, the I Army Corps left Minsk on 12 July 1812 to cut off Pyotr Bagration from Barclay de Tolly.