During the War of the Fifth Coalition Rottembourg led the 108th Line in Louis Friant's 2nd Division in Marshal Louis-Nicolas Davout's III Corps. The regiment started the campaign with 2,189 men in three battalions. Friant's division took part in the Battle of Eckmühl on 21–22 April 1809. The 108th Line also fought at the Battle of Wagram on 5–6 July. By that time the regiment's strength was reduced to 1,724 men. On the second day, while some of Davout's divisions assaulted Markgrafneusiedl, Friant's division and its supporting cavalry advanced to the north of the village. After bitter fighting the Austrians were compelled to retreat. Rottembourg was wounded on 6 July. He became a Baron of the Empire on 20 August 1809 and received promotion to general of brigade on 21 July 1811.