On 25 March 1814, Collaert commanded the 5th Heavy Cavalry Division in Milhaud's cavalry corps. The division was made up of a 1,037-strong brigade that included the 2nd, 6th and 11th Dragoons and an 872-man brigade that counted the 13th and 15th Dragoons. He led a brigade consisting of the 22nd and 25th Dragoons in Lhéritier's 6th Heavy Cavalry Division during the Battle of La Rothière on 1 February 1814. Led by Gebhard Leberecht von Blücher, 80,000 Allies defeated Napoleon's 45,000 French troops. In response to the initial attack by Fabian Gottlieb von Osten-Sacken's Russian army corps, Lhéritier charged but was slowed by wet ground and stopped by intense artillery fire. After heavy fighting, the division was employed in covering the retreat of the French army.