The Swedish victory seemed assured, when a mighty trampling of horse was heard, and emerging from the smoke Pappenheim with eight regiments of Imperial cavalry dashed into the fray.
Pappenheim had already captured the citadel of Halle when Wallenstein's messenger reached him.

To wait until his infantry, who were engaged in plundering, could be collected, and then to proceed at their pace to the field of battle, would be to arrive too late to be of service, and Pappenheim instantly placed himself at the head of his eight regiments of magnificent cavalry, and galloped at full speed to the battlefield eighteen miles distant.

On the way he met large numbers of flying Poles and Croats, the remnants of the Austrian left, who had been driven from the field by Gustavus; these he rallied, and with them dashed upon the troops of Stalhaus who were pursuing them, and forced them backward.
The relief afforded to the Imperialists by this opportune arrival was immense, and leaving Pappenheim to deal with the Swedish right, Wallenstein rallied his own right on the centre, and opposed a fresh front to the advancing troops of Duke Bernhard and Kniphausen.
Inspirited by the arrival of the reinforcements, and burning to turn what had just appeared a defeat into a victory, the Imperialists advanced with such ardour that the Swedes were driven back, the guns on the hills recaptured, and it seemed that in this terrible battle victory was at last to declare itself in favour of the Imperialists.
It needed only the return of Pappenheim from the pursuit of the Swedish right to decide the day, but Pappenheim was not to come.

Though driven back by the first impetuous charge of the Imperial cavalry, the Swedes under Stalhaus, reinforced by the Scottish regiments under Henderson, stubbornly opposed their further attacks.
While leading his men forward Pappenheim fell with two musketballs through his body.

While lying there the rumour for the first time reached him that Gustavus had been killed.