In 1792, he became proprietor of the "Mészáros" Uhlan Regiment (this became # 1 in 1798) and held this dignity until 1797. The mounted lancer unit was formed by combining two uhlan squadrons each from the "Kaiser", "Karaczay", "Levenehr", and "Lobkowitz" Chevauxleger Regiments. On 13 October 1793, he led the 4th column under Dagobert von Wurmser in the First Battle of Wissembourg. He was awarded the Knight's Cross of the Military Order of Maria Theresa on 25 October 1793 for his distinguished service. In 1794, he served in Friedrich Freiherr von Hotze's corps. Promotion to Feldmarschall-Leutnant came on 4 March 1796 after more service with the Army of the Upper Rhine under Wurmser and Maximilian Baillet de Latour. He received the Commander's Cross of the Military Order of Maria Theresa on 11 May. On 5 July 1796, Mészáros and Karl Aloys zu Fürstenberg led the Austrian rear guard in action at Rastatt.