The Battle of Mannheim (18 September 1799) was fought between an Austrian army commanded by Archduke Charles, Duke of Teschen and a French army under Jacques Léonard Muller. Most of the French Army of the Rhine had retreated to the west bank of the Rhine River, leaving the division of Antoine Laroche Dubouscat to hold Mannheim on the east bank. Despite assistance by Michel Ney, Laroche's division was beaten and driven out of the city when attacked by Charles and a much superior force. The War of the Second Coalition action occurred in the city of Mannheim, today located in the state of Baden-Württemberg in southwest Germany about south of Frankfurt.
In the summer of 1799, Muller's 18,000-man army had the mission of drawing Charles' Austrian army away from Switzerland, the central and western portions of which were held by André Masséna's army. Moving south from Mannheim, the Army of the Rhine laid siege to Philippsburg. Provoked by this threat to his strategic rear, Charles and 30,000 troops moved north against Muller, who quickly withdrew. Muller erred in leaving Laroche to be mauled by Charles, but his campaign became a strategic success when Masséna severely defeated a Russian army at the Second Battle of Zurich on 25 and 26 September.
Background
On 4 June 1799, the First Battle of Zurich was fought between André Masséna's 45,000-strong Army of the Danube and a 53,000-man Austrian army led by Archduke Charles, Duke of Teschen. Austrian casualties numbered 2,400 and eight guns while the French lost 4,400 men and 28 guns. Though the French held their ground, Masséna evacuated Zürich the next day and withdrew to a strong position overlooking the city. Altogether, Masséna commanded 76,781 troops. In Switzerland were infantry divisions under Claude Lecourbe (1st), Joseph Chabran (2nd), Jean-de-Dieu Soult (3rd), Jean Thomas Guillaume Lorge (4th), Jean Victor Tharreau (5th), François Goullus (6th), Joseph Souham (7th) and Louis Marie Turreau (Valais), a cavalry division under Louis Klein and an infantry reserve under Jean Joseph Amable Humbert, plus occupation troops. The 6th and 7th Divisions were supervised by Pierre Marie Barthélemy Ferino while Lecourbe controlled the 1st and 2nd. Included in Masséna's command were Claude Juste Alexandre Legrand with 6,186 men and Claude-Sylvestre Colaud with 5,106 men watching the Rhine north of Strasbourg. Opposed to the French were 85,000 troops led by Charles, including a force watching the French divisions on the Rhine to the north and eight battalions under Gottfried von Strauch near the Saint Gotthard Pass in the south.
The Army of the Rhine was formed on 5 July 1799 by Jean Baptiste Bernadotte, who was the Minister of War. The army was responsible for an area along the Rhine River from Neuf-Brisach on the south to Düsseldorf on the north, including the fortresses of Breisach, Kehl, Strasbourg, Landau, Mannheim, Mainz, Ehrenbreitstein and Luxembourg. The French reported the strength of the army as 40,000 to 60,000 men, but this was a ruse to trick the Austrians. In fact, much of the army's strength was tied up in garrisons and it is unlikely that the number of troops available for field operations exceeded 18,000. The purpose of the Army of the Rhine was to lure the Austrian army away from Masséna. This could be achieved by menacing Archduke Charles' supply line, which ran northeast from Switzerland to Ulm on the Danube River. The army was too weak to fight the Austrians in a pitched battle, but it was enough of a threat that it could not be ignored.
Meanwhile, an Austro-Russian army under Alexander Suvorov had cleared most of Italy of its French occupiers. In the Battle of Novi on 15 August 1799, the Allies suffered 8,200 casualties, mostly Austrian, but chased the French army back into its last narrow slice of Italian territory near Genoa. During this time, the Austrians were very successful in reducing the French-held fortresses in Italy. By 11 September, the only Piedmont fortress that remained in French hands was Cuneo.