The 40th was part of the 3rd Division of Lannes' V Corps of the "Grande Armée" during the War of the Third Coalition and Michel's services at the battle of Austerlitz earned him, on December 27, 1805, the rank of Colonel and his admission, and transfer to, the 1st Regiment of Grenadiers of the Imperial Guard, on 1 May 1806. He took up the post of Major in the 1st Grenadiers as everyone serving in the Guard was considered to be a rank above those in the line infantry.