When the War of the Second Coalition began in early 1799, Nauendorf fought in the Austrian victories at Ostrach (21 March) and then at Stockach (25 March). In early March he led the advanced guard of 17,000 across the Lech River by Augsburg, to deploy at Ostrach, a village about of the Danube River and less than from the Free Imperial City of Pfullendorf. Jourdan's Army of the Danube had crossed the Rhine on 1 March, and moved east to cut communication between the main Austrian force, quartered near Augsburg, and the Austrian troops in northern Italy. At Ostrach, his advanced guard sustained the immediate shock of contact, but the main force of the army was less than a day behind him, and Archduke Charles, the commander of the Austrian force, divided his army into three assault columns to make a simultaneous attack at three points on the French line; after a day of nasty fighting, the Austrians flanked the French at the north and south, and threatened to break through the line in the middle. The French withdrew to Mösskirch, and then to Engen and Stockach, where, on 25 March, the fighting renewed. At Stockach, Nauendorf again commanded the Austrian advanced guard, which was composed of troops seasoned, as he had been, in the Habsburg border wars. The advanced guard, or "Vorhut", was redeployed before the battle as the center of the main Austrian line, and took the brunt of the initial fighting.