Marcognet received promotion to Adjutant General (colonel) in the 108th Line Infantry Demi-Brigade on 18 June 1800. At the Battle of Hohenlinden on 3 December 1800, the 2,234-strong 108th Line served in Emmanuel Grouchy's division of Moreau's army. As the head of Johann Kollowrat's Left Center Column advanced along the main highway from the east, they bumped into Marcognet's 108th Line at about 7:00 AM. He deployed his troops in line along the edge of a forest. Franz Löpper, who led the Austro-Bavarian advance guard, immediately ordered his 5,341 foot soldiers and 1,319 cavalrymen to attack. Showing tactical finesse, Marcognet repulsed the first attack by the "Benjowski" Infantry Regiment Nr. 31 with the help of the 4th Hussars and three cannons. Outnumbered two-to-one, he was holding his ground when enemy reinforcements arrived. Using a forest trail, Lelio Spannochi secretly posted the "Sebottendorf" Grenadier Battalion on the flank of the 108th Line and charged. Surprised, the French rapidly retreated leaving the wounded Marcognet to be captured.