south, away from Blücher. On 5 February, Russian General Michael Andreas Barclay de Tolly ordered Seslavin's force away to the extreme left flank without notifying Blücher. Over the next few days, the Prussian field marshal mistakenly continued to believe that Seslavin watched the gap on his left flank. At this time, Napoleon began to consider the possibility of moving against Blücher's army. The French emperor calculated that Marshals Claude Perrin Victor and Nicolas Oudinot with 39,000 troops would be able to hold off the cautious Schwarzenberg. Meanwhile, Napoleon gathered a strike force of 20,000 infantry and 10,000 cavalry and prepared to march against Blücher. By 8 February, Blücher's advancing Army of Silesia spread itself out across . Farthest to the west was Sacken's cavalry at Viels-Maisons while his infantry was at Montmirail. The Russian was in pursuit of Marshal Jacques MacDonald's 10,000-man French corps. Also following MacDonald was Yorck's corps which reached Dormans to the northeast of Montmirail. Olsufiev's 4,000-man corps was east of Sacken at Étoges. Peter Mikhailovich Kaptzevich's Russian corps and Friedrich von Kleist's Prussian corps were farther east at Châlons-sur-Marne. On 9 February, with everyone marching west, Kaptzevich and Kleist reached Bergères-lès-Vertus, Olsufiev arrived at Champaubert, Sacken got to La Ferté-sous-Jouarre, and Yorck approached Château-Thierry. Prussian staff officer Karl Freiherr von Muffling wrote that Sacken had 20,000 soldiers and Yorck's corps numbered 18,000 men while Olsufiev, Kaptzevich and Kleist together counted 19,000 troops. Another source gave Sacken strength as 16,000. On 9 February, Napoleon arrived at Sézanne with the Imperial Guard after a difficult march over muddy roads. French farmers brought their teams of horses to help pull the cannons through the quagmire. That day, Schwarzenberg asked Blücher to reinforce his right wing. Dutifully, the Prussian commander set out on 10 February with Kaptzevich and Kleist, moving southwest toward Sézanne. As the Allies marched, they heard the distant growl of cannons to their right. It was Napoleon's army falling on Olsufiev's outnumbered corps in the Battle of Champaubert. After an obstinate resistance, Olsufiev tried to break out to the east, but he was captured and his corps effectively destroyed. During the fighting, Olsufiev sent several messengers stating that he was under attack, but Blücher ignored them. The 1,500 Russian survivors of the debacle were organized into 3–4 combined battalions. This hard-luck outfit would suffer 600 casualties and lose all its remaining cannons at the Battle of Vauchamps