The Russians marched in two columns, which lost touch of one another, and as it was quite impossible for either to engage the French singlehanded, they both retired again towards Smolensk, where with an advanced guard in the town itself - which possessed an oldfashioned brick enceinte not to be breached by field artillery alone - the two columns reunited and deployed for action behind the unfordable Dnieper.
The weather had become bad, and the Nive unfordable; but there were additional and serious causes of delay.
Moltke, knowing well the danger for a great army of being forced into a battle with an unfordable river behind it, and with his naturally strong bent towards the defensive in tactics, concluded that Benedek would elect to hold the left bank of the Elbe, between the fortified towns of Josephstadt and Kiiniggra,tz, with his right thrown back and covered by the lower courses of the Aupa and the Mettau.
Instead of concentrating his force upon one bridge over the swampy and unfordable Dyle, Grouchy scattered it in attacks upon several; and when the emperor's despatch arrived, saying Billow was in sight, the marshal was powerless to move westward.
The river formed an unfordable barrier and also a useful means of communication.