At dawn on 12 February, Sacken's corps passed through Yorck's lines near Montfaucon. Sacken dropped off a brigade under General Heidenreich that consisted of the Tambov and Kostroma Regiments. Friedrich von Katzler's advance guard stood at Montfaucon with the 1st and 7th Prussian Brigades and the Reserve cavalry of Georg Ludwig von Wahlen-Jürgass in support. Mortier marched to Fontenelle-en-Brie with the 2nd Old Guard Division under Charles-Joseph Christiani, the 1st Voltiguer Division under Claude Marie Meunier, and the Gardes d'Honneur cavalry. Napoleon had Saint-Germain with 2,400 cavalry and Louis Friant's 1st Old Guard Division. At 1:00 pm, Mortier's advance encountered Katzler's Prussians near Viffort and the Caquerets Hills. Katzler's 1st and 2nd East Prussia Infantry Regiments overlooked a stream. The position was attacked by two battalions of Old Guard Foot Chasseurs and Napoleon's duty squadrons led by Claude-Étienne Guyot. Katzler withdrew when the French began turning his flanks.