This map shows the situation as known to both armies as at midnight 3 April 1813.
The Prussians have established themselves on the west bank of the river Elbe between Salzwedel and Bismark.
A third Prussian corps at Parey is pinning the French at Colbitz and threatening Magdeburg.
The northern French corps at Domnitz is in real danger of being cut off from the main French army. Their supply lines are not in danger as they can draw on Hamburg, which is off map top left.
The French Army headquarters has moved north to Ruhen to keep in touch with the northern corps. However they are within one day’s march of Prussian cavalry at Kalbe and in danger of being captured.
French reinforcements are arriving from Hanover, and are well concentrated to strike at the Prussian left flank.
The Prussians have seized the initiative and crossed the formidable river crossing unopposed. They must now decide whether to strike north or south, of risk moving through the mountains in the centre.