Defrance also served in the Swiss Campaign of 1799 as divisional Chief of Staff of the 1st Division of Jean-Baptiste Jourdan's Army of the Danube; after the losses at the battles of Ostrach and Stockach in March 1799, the Army of the Danube was combined with the Army of Helvetia, under the command of Andre Massena. Defrance continued in his capacity as divisional chief of staff. At the First Battle of Zurich in June 1799, he was appointed on the field as brigadier general, an honor which he declined, asking instead to be given command of a cavalry regiment. He received command of the 12th Regiment of "Chasseurs-a-Cheval." As "Chef-de-Brigade", the equivalent of colonel in France's revolutionary-era field army, Defrance went to Italy and participated in the actions leading up to the Battle of Marengo. During the winter of 18001801, he campaigned in the Grisons in Switzerland and returned to France after the Treaty of Lunéville in 1801.