In 1800, he was appointed deputy commander of the main army in southern Germany, which ended in disastrous defeat at Hohenlinden in December.

During the Austro-Turkish War (1787-1791) he earned appointment to the rank of General-Feldwachtmeister and the Knight's Cross of the Military Order of Maria Theresa for his distinguished actions at the Siege of Belgrade in 1789.

For notable actions in capturing the Neckerauer redoubt on 30 October, he earned the Commander's Cross of the Military Order of Maria Theresa.

[4] On 19 August, Emperor Francis II ordered Wurmser to make another attempt to relieve the town and named Lauer as his chief-of-staff.

When drawing up the plan of attack, Lauer assumed that losses would prevent the French from quickly reacting to an Austrian offensive.

After overwhelming Paul Davidovich's covering force at the Battle of Rovereto, the French commander sent his troops marching east, then south down the Brenta River valley.

[2] When the War of the Second Coalition began in 1799, Archduke Charles, Duke of Teschen asked that Lauer be returned to field service.

[7] During the campaign of spring 1800 in Southern Germany, a well-organized and equipped French army of 108,000 under Jean Victor Marie Moreau faced an Imperial force of 120,000 commanded by Pál Kray.

Although slightly larger, Kray's army included troops of lower quality and the Austrians were driven from the Rhine to the Inn River.

Instead, Francis selected Charles' inexperienced 18-year-old brother, Archduke John of Austria as commander, and made Lauer his second-in-command, calling him "the most innovative man in the art of war".

[10] Francis chose John hoping that his status would end the tendency of senior officers to discuss orders and obey them only if they agreed.

At the same time, he expected John to remain a mere figurehead while Lauer made the important decisions, creating a very awkward command structure.

[11] Bonaparte decided peace talks were not yielding the results he wanted and on 12 November notified the Austrians the armistice would end in 15 days.