Loison became a Grand Officer of the Légion d'Honneur on 14 June 1804. During the Ulm campaign in 1805, he served in the VI Corps under Marshal Michel Ney at the Battle of Elchingen. Austrian general Johann Sigismund Riesch held Elchingen with a force numbering 8,000 soldiers, including 14 battalions, 11 squadrons, and 12 guns.