The engagement of Mormant (17 February 1814) saw the French defeat part of the Allied cavalry at the start of Napoleon's most effective attack on Schwarzenberg's Army of Bohemia during the campaign of 1814.
After defeating the French at La Rothiere (1 February 1814) the Allies decided to take seperate routes to Paris. Blucher's Army of Silesia was to move north and advance along the Marne, while Schwarzenberg's Army of Bohemia was to push down the Seine. The Allies expected Napoleon to stop on the Seine, but instead he dashed north and inflicted a series of defeats on Blucher, a period known as the Six Days Campaign. While Napoleon was winning around the Marne, his forces on the Seine were being forced back by Schwarzenberg. Victor and Oudinot had been unable to hold Nogent, Bray and Pont-sur-Seine, and were forced to retreat north towards the River Yerres, a tributary of the Seine.
Napoleon began to send troops south towards the end of the Six Days Campaign. Macdonald and Kellermann were sent to join Oudinot on 13 February, and reached Guignes on the Yerres on 14 February. The final battle of the Six Days, at Vauchamps (14 February 1814) was triggered by Blucher's attempt to stop Napoleon moving south, but Blucher suffered another heavy defeat and decided to retreat east towards Chalons-sur-Marne. Marmont was sent to watch Blucher, while Grouchy and the Guard were orderd to follow Macdonald down the roads towards Guignes.
On 15 February Schwarzenberg stopped his advance, worried that Napoleon was now heading his way. On the same day Napoleon left Montmirail at the start of an impressive forced march, leaving Marmont and Mortier to defend the Marne. Victor, Oudinot and Macdonald were ordered to hold the Yerres for 72 hours. Napoleon reached Guignes at 3pm on 16 February, and prepared to go onto the offensive.
On 16 February the Allies had four corps in the danger area. On their left Bianchi was south of the Seine, with his advance guard in Fontainebleau and the main part of his corps further up the Seine. Next in line were the Wurttembergers, who were centred around Montereau on the Seine. To their right Wrede's Bavarians were at Donnemarie-Dontilly (north-west of Bray), with one division further north at Nangis. On the Allied right Wittgenstein had his main force in Nangis, with his leading troops further to the north-west at Mormant.
On the French side Oudinot's VII Corps was around Guignes, north-west of Mormant. Victor's II Corps was at Chaulmes, a little further to the north-east. The Guard, which had come south with Napoleon, was a little further north-east, at Fontenay. Macdonald's XI Corps was at Solers, to the west of Guignes, forming the right wing of the main French concentration.
The French offensive began on 17 February, and swept away several Allied formations in the area between the Seine and the Yerres. Napoleon's plan was to capture the bridges at Montereau and Bray and catch Schwarzenberg while his army was still scattered and before Blucher could come to his aide. On the Allied side Schwarzenberg had issued orders to a retreat back to Troyes, where he planned to unite with Blucher and then resume the march on Paris.
The first significant fighting on 17 February came at Mormant, where Wittgenstein's advance guard, under General Pahlen, hadn't received the order to retreat in time. Pahlen had 10 infantry battalions, four regiments of Cossacks and 14 cavalry squadrons in his force. He found himself in the path of Gerard's division from Victor's corps, with the rest of the corps close by, and Napoleon present in person. Gerard's infantry forced the Russian infantry to retreat from Mormant. This exposed them to attack by the French cavalry, and many were captured. Kellermann and Milhaud were then sent to attack both flanks of the retreating force, again with great success.
Pahlen's infantry suffered under repeated French cavalry attacks, and by the end of the fighting Pahlen had lost 2,114 infantry and one third of his cavalry. The French lost less than 200 men.
After their success at Mormant, the French were split up to pursuit the retreating Allies. Oudinot's VII Corps was sent east towards Provins and Nogent. Macdonald's XI Corps was sent towards Donnemarie to press Wrede's Bavarians. Victor's II Corps was sent towards Villeneuve-les-Bordes, along the road from Nangis. This brought them into direct contact with Wrede's advance guard near Valjouen, where Gerard won a second victory.
In the aftermath of these two victories Victor and the Guard were ordered to march to Montereau on the Seine. Victor ignored his orders to march through the night, allowing Wurttemberg to arrive from the west and take up a fortified position north of the Seine, covering Montereau. Napoleon was furious with Victor, and replaced him as corps commander by Gerard. Gerard then had the task of taking Montereau, and was in command for the first part of the battle there on 18 February.