Indeed the Russian army had begun to move in the first week of April. After the French retreat from Smolensk in November, General Bennigsen's army had linked up with those of Barclay and Wittgenstein, but due to the overcrowding at Borisov, had Wintered in Smolensk. By April these three forces in total numbered around 170,000 men, facing hardly 30,000 Franco-Allied troops. In all likelihood all that was needed was a simple frontal attack, there was no stroke of tactical genius that would allow victory against odds of more than five to one.
In fact this seemed obvious enough that for once, both Kutuzov and Barclay were in complete agreement about a cautious but steady advance on Minsk, but the Tsar objected. He insisted that nothing but the total annihilation of the foreign invader would buoy the morale of the Russian Army and people, and ordered a plan that could achieve that. Somewhat reluctantly, Kutuzov drew up a plan for Barclay to carry out. Using Cossacks under Platov in the North and Karpov to the South, they would screen their movements from the French. These forces forded the Berezina near Kimiya and Byerazino on April 1st.
The next day around 50,000 men each under Wittgenstein in the North and Bennigsen in the South followed them on pontoon bridges, while the rest of the Army under Barclay and company crossed at Borisov. The plan did achieve its goal on its face, Bessiéres had no idea the number nor composition nor movements of the Russian infantry. However, thanks to the efforts of General Grouchy and his cavalry (Who were even more severely outnumbered than the infantry) Bessiéres knew that the army was likely crossing in force. Despite having no permission from Napoleon to do so, the French left Minsk on the 4th, 28,000 fighting men, and 115 guns. Barclay reached the city just later that day, and launched a frantic pursuit against the French.
Bessiéres decided to keep retreating the way they'd come, to Vilnius, where he hoped to resupply one last time before falling back to cover Warsaw. As he did so, the Cossacks attacked in force, but without infantry support could do little but slow the French down. The retreat soon became another race, as both sides sprinted to try and outrun eachother. Barclay and Bessiéres both knew the latter couldn't afford a protracted battle, and both sides thusly strove to prevent it. However the going was tough both sides, as the rasputista (The mud caused by Autumn rain and spring thaws) was in full swing, fed by melting snow and thawing ground. Wagons and guns got stuck and were abandoned, horses broke their legs falling in the muck. Both sides trudged through it, until finally Bessiéres luck ran out.
Russian partisans had burned the bridge over the Oshmyanka river at the town Oshmyany (OTL modern day Ashmyany) in an attempt to stop the French. Bessiéres arrived on the 13th, and quickly drove out said partisans, getting his engineers to work rebuilding them. The Russians arrived at around 3pm, before they were completed. For two hours the French resisted artillery and relentless Cossack attacks, forming square among the farmhouses to keep them at bay. At 5pm the bridges were ready, and Grouchy and Poniatowski's V Corps crossed over. As Davout's Corps began to cross next, the French lines broke as Russian guard cavalry and infantry arrived (The Russian army had been strung out as it attempted to catch the smaller French army). Ney led his III Corps, amongst the fireband chaos rallying the men in the streets and attempting to organize them. However in the twilight and confusion around 8pm, a French Corporal mistook some French scouts for Cossacks, and detonated the gunpowder under the bridge, cutting off Ney and around 7,000 men.
~~~~~~~~~~~~~
When I find that Corporal, I swear to Christ Marshal Ney thought, rage filling him. A heavy wind was blowing both his mens powder and that of the Russians back in his face, making the red twilight even dimmer. "Goure!?" he shouted over the din of cannon fire and screams of the wounded "Any chance we can swim the river!?" His chief of staff shook his head with despair "No sir, that water is freezing and it's getting dark. Even if the men could survive we'd have no powder, and look!" Through the smoke and noise, Ney could here the bugles and see the guns limbering up "That fucking bastard is leaving us! How very fucking Christian of him!" He threw his telescope on the ground in rage "If I ever see that man again, I'll slap the fucking powder out of his hair!"
Just then, one of his aides rode up to him, a hussar with a white flag in tow "Agh Christ." He muttered under his breath "The hell do you want?" "Marshal Ney" the trooper said in awful French "His Majesty Tsar Alexander and General Barclay send their complements. You and your men have fought well today, and honor is satisfied. I beg you, surrender to his majesty now, and your wounded will receive our aid, and your men will be well treated." "Does he now?" Ney said with a sly grin, which just as quickly vanished "Tell your Tsar this. All the Russians and Cossacks in the world will not prevent me from rejoining the army. Now get out of here, before someone doesn't see that flag." The hussar, stunned, did as he was told. "Now then!" Ney called out "You want to live!?" He picked a musket up from a dead soldier near him "Grab a weapon and follow me!"
~~~~~~~~~~~~~
Sure enough, Ney rallied about 4,000 men, and led them on foot out of the town. With few options but to charge through the Russian lines, they did so, but were mown down. Still refusing to surrender, Ney formed square with the survivors and marched onward, looking for a crossing upriver. Stumbling through the dark, and with their musket flashes being the only light source, which often illuminated hordes of Cossacks surrounding them, Ney pressed on. That night, about eight miles upstream, the men found a ford shallow enough to cross without getting soaked. Despite his rearguard being down to just 300 men, Ney made contact with friendly cavalry at dawn, and managed to rejoin the army at about noon. It had come at terrible cost, but they escaped a situation where any other commander would've surrendered.
Ney was so furious at Bessiéres that when they reunited that day, they nearly came to blows. Nonetheless, Napoleon was so impressed when he heard the feat, that he exclaimed "What a soldier! The army is full of brave men, but Michel Ney is truely the bravest of the brave!" News of teh Marshals escape spread, and the men rejoiced happy in spite of the relentless, muddy marching. They army arrived in Vilnius four days later, where they received fresh food, ammunition, and 6,000 reinforcements. They couldn't stay long however, Barclay was right on his heels, and so he was forced to retreat back toward Warsaw.
The remnants of the army crossed the Niemen river back into Polish territory on the 23rd. According to legend, Marshal Ney was the last man across. Without a Corps to speak of, he was sent back to France to take charge of a new III Corps, still forming out of the new recruits. The invasion of Russia had been a disaster for Napoleon, one that had cost him half a million men, a quarter million horses, and over a thousand guns. In exchange the war was where it had been nearly a year before, and now the Russian bear had woken up. With Poland all but open to the enemy, and Napoleon's German allies wavering, the fate of Europe was about to be decided.
