After dispatching Blücher’s Army of Silesia at Vauchamps, Napoleon diverted temporarily toward the Seine at Montereau, for an inconclusive brush with Schwarzenberg’s Army of Bohemia. Blücher received reinforcements from the Army of the North, and soon was threatening Paris.
Cutting short his operations in the south against the Army of Bohemia, the Emperor set out on an 80-mile, three-day march toward Blücher’s last known location, La Ferté sous-Jouarre on the Marne. While Macdonald’s 42,000 men contained Schwarzenberg, his force of 35,000 would steal a march on the Prussians.
On March 1st, Napoleon’s sudden appearance on the Marne forced Blücher to break off the action and retreat toward Fismes on the 2nd. The Emperor was unable to get the bridge at La Ferté repaired until the 3rd.
Blücher welcomed tidings of two strong allied corps on their way to join him—just in time, as the Silesian Army was beginning to unravel. The bonds of discipline showed signs of strain under recent losses; baggage and wounded were falling by the wayside.
These two fresh corps under Bülow and Winzin-gerode captured Soissons, opening a line of retreat north over the Aisne river for Blücher. Had Soissons held out for another day, Napoleon might have arrived in time to interfere with the rearguard at Fismes, although Blücher would probably have escaped. The retreat went smoothly and all his troops were across by the morning of the 5th.
After crossing at Soissons and at Vailly (S3219), Blücher deployed along the north bank of the Aisne, while Napoleon moved to outflank him, seizing the stone bridge at Berry-au-Bac (E1205), to march upon the ancient cathedral city of Laon (N0719).