1812-04-02.
It would become known as 'the German dash' or alternatively 'the French wiggle' and would be studied for decades, if not hundreds of years as a masterpiece of manouvre warfare at the same levels as the Grodno campaign of 1706, even though it was less decisive.
Basing himself in Saxony, Napoleon had fed his troops well, absorbed reinforcements, raised Polish troops and recieved a surprising amount of stragglers - the last French troops rejoining his troops are said to have been a group of dehorsed Hussars and light infantrymen, a dozen men in all that emerged from the Pripyat marshes in laye July to join him in August!
Correctly judging that the Austrians would not move from Bohemia until they had more troops, Napoleon sent Macdonald and Ney with roughly 30 000 men eastward from Leipzig. In mid-april they silently entered Dresden, crossed the Elbe and fell over the advance guard of Kutuzov, a Corps under command of Bulatov.
The Russian troops were caught unawares, and in a single day sharp action they were routed almost to a man, and Bülow and his Prussian II. Corps could only help repel the pursuing French cavalry and allow Bulatov's forces to reform.
Having temporarily stopped the Russian army in its tracks, drawn off parts of the best of the Prussian forces at a meagre cost of some 2 000 causalties, cuasing the Russians nearly 8 000, Macdonald and Ney retreated back over the Elbe, burning its bridges behind them.
In the meantime, Napoleon sent his fresh Polish recruits northwards along the east bank of the Saale river into Brandenburg, looting and attacking the local militia. As intended, this drew the ire of the ever aggressive von Blücher, who rushed out with roughly half the Prussian army and a large force of militia, a force of some 60 000 in total, brushing the inexperienced Polish cavalry aside before running headlong into the trap Napoleon had prepared for him. On the first of May 1812, Napoleon himself trashed von Blüchers force just nort of Halle, casuing the Prussians just above 9 000 casualties, while suffering less than 3 000 of his own.
At the same time, Davout had rushed ahead out of the Rhine Confederation, bringing the best troops, most of the cavalry and in the process sucking up all French and other veteran troops of Bernadotte's Corps - to the latter's vain protests - to deal with af Klercker and his Swedish army slowly advancing southeast from Pommerania.
45 000 French, of which more than 15 000 were cavalry (most of which were intended to replace Naploen's depleted cavalry force) crashed into the Swedes on the 3rd of May 1812.
While af Klercker is usually considered a good general, if somewhat catious, that always kept his options open, he was certainly no Davout. Commanding a joint force of some 50 000, including 1 000 British, 2 000 Danes and 10 000 Prussians (a mix between militia and regular forces) he occupied a ridgeline, erected some rudimentary field fortifications and had his light infantry erect hinders of sharpened poles dug into the ground at the flanks to prevent the superior French cavalry from flanking him.
At that day, the Swedes learned the hard way the superiority of a Napoleonic grand battery of light-weight but strong 12pdr guns over their spread.ut 3pdr guns and smaller supporting battery of 6pdr and heavier 12pdr guns.
The rudimentary earth works could not resist the French fire, and soon the Swedish line was buckling - before ther French line infantry had even reached it. The fight was short and soon the Swedish army was routing through the entire line. It was only the preserverance of Finnish-speaking Jäger light infantry and veteran gunners manning 3pdr guns moved around like pistols in the retreat as well as the French cavalry either having to navigate a their own troops which had become disorganised in the retreat or the by now abandoned sharpened stakes that saved the Swedish army from complete annihilation at the hands of Davout and his army.
The stand of the Prussian militia in a forest on the Swedish right flank also helped, as did the fact that Davout considered the Swedish army the lesser threat - he was in a hurry to join forces with Napoleon in Saxony and bring him horses for his dehorsed cavalry - there was no time to pursue and destroy the Swedish army.
Davout's mnen suffered only around 1 000 casualties, while the Swedish army and its allies suffered more than 7 000 in total.
While Napoleon and Davout had inflicted a series of stinging defeats on the allies of the fifth coalition, there was a big difference compared to the campaigns of 1805, 1807 and 1808. While the allied armies were defeated, they kept together and kept in the field. Despite his victories, Napoleon could not force any of his enemies' armies to quit the field and dissolve. And the strategic situation remained the same, even if the Prussians, Russians and Swedes were licking their wounds, they were all relatively close to their sources of men and supply and could replace their casualties. Napoleon could not in the same way.