On the death of Emperor Henry VII two rivals claimed the crown: Ludwig of Bavaria and Frederick the Handsome of the House of Habsburg. After a double election, clashes occurred under the walls of Aesling, which was allied with the other cities in the high Neckar. Ludwig declared himself their protector, and was joined by John, King of Bohemia and by troops of the Elector of Trèves. The Swabian towns were called upon to supply contingents of foot, as were those in the Rhineland. Ludwig marched into lower Bavaria, and soon encountered Frederick on the right bank of the River Inn near the town of Mühldorf. Frederick is said to have had as many as 30,000 men including not only his own Austrian forces but also numbers of Hungarians and Cumans. Ludwig was perhaps stronger in numbers, and was eager to force a battle as Frederick’s brother, Leopold was about 18 miles away with reinforcements.
Having spent the night of the 21st September at the castle of Dornberg, Ludwig decided to attack the following morning. His army was drawn up in four divisions, as was that of his adversary. Ludwig wore a blue surcoat with a white cross, and took position among his Bavarian knights. On the opposing side Frederick commanded personally while his younger brother Henry led another troop under the Austrian banner.
The fact that Frederick accepted battle has puzzled many historians. It has been suggested that his retreat was cut off, or that he was overconfident and expected his brother to arrive in time. As it happened, Leopold delayed while ravaging the borders of the Lech, and never arrived to join the fighting. Matters are complicated by addition of legendary tales to rather obscure evidence. On the left wing of Ludwig’s army the Bohemian and Silesian knights of King John clashed with the Austrian and Tyrolian troops of Henry. In the combat that followed Henry was at one point thrown from his horse. As midday approached the Austrians began to push back the forces under Ludwig. It was now that the Bavarian foot were brought into action. Led, according to legend, by a native of Franconia called Siegfried Schweppermann, the burghers of Munich and a number of dismounted horsemen came upon the Austrians and cut a path into their ranks. Ludwig was only narrowly saved from capture.
As the battle began to turn the Burgrave Frederick of Nuremberg, held in reserve by Ludwig and (so it is asserted) wearing Austrian colours to deceive Frederick, was launched with 500 knights against the disorganized enemy. This proved too much; the Hungarians and Cumans in the rear turned and fled. Frederick refused to flee, wishing to die with honour. A lance thrust felled his horse and he was forced to surrender to Frederick of Nuremberg. One Austrian account asserted that 500 Bohemian cavalrymen had surrendered, but broke parole to assist the Burgrave. Austrian losses are estimated to have been around 1,300. Frederick was imprisoned for three years before becoming joint emperor with Ludwig.