In the War of the Third Coalition, Gazan initially was assigned as a division commander of Napoleon's Grande Armée in Lille, in preparation for the planned invasion of England; he remained there until the idea was abandoned. In August 1805, Gazan commanded of a division of the army that encircled Austrians in Ulm. On November 11, under Marshal Mortier, his division provided the advance guard in the march against Kutuzov's army. As they advanced through a narrow Danube canyon, the division was isolated from the main force, near Dürenstein. By the small village on the Danube, famous as the prison of Richard the Lionhearted at the end of the twelfth century, he and his division were trapped in a narrow canyon, attacked by a Russian force at his rear and more Russians at his front. Gazan's division fought desperately for a harrowing day and suffered 40 percent casualties. He and Mortier were finally rescued by the arrival of the VIII. Corps' 1st Division, commanded by Pierre Dupont de l'Étang, but only after the loss of nearly 4,000 men. In addition, 47 officers and 895 men were captured, and he lost five guns, as well as the eagles of the 4th Infantry Regiment, and the eagle and guidon of the 4th Dragoons. As recognition of his conduct in "the immortal Battle of Dürenstein," he received the Officers Grand Cross of the Legion of Honor and the survivors of his division was sent to Vienna to recuperate. When Austria sued for peace, Gazan's division was sent to Würzburg in Bavaria, where it remained until Prussia declared war in October 1806.