Allons enfants de la Patrie, le jour de gloire est arrivé!

On December 14th of 1812, Napoleon's retreating Grande Armée finally left Russian territory. The original invasion force exceeded 650,000 men from all across Europe, only 355,000 of which were French: over 50% of the Grande Armée was foreign, filled with Belgians, Dutch, Germans, Italians and many others. Popular "legend" in France says that Napoleon left Russia with 22,000 survivors from the Grande Armée. Excluding the traitorous Austrian and Prussian contingents (50,000 all told) who had refused to fight and stayed in eastern Europe, but including the secondary French armies that remained behind to protect supply lines and occupy major Russian cities, Napoleon managed to save less than 100,000 of his men, putting casualties somewhere in the realm of 80% (but potentially over 90%, at worst).
This Russian Disaster quite obviously destroyed the French army. Only 27,000 Grande Armée survivors remained fit to continue duty; 380,000 men had died, another 100,000 if not more became prisoners (and half of these died in Russian captivity). France's horses, some of the best mounts in the world raised in Normandie, froze to death; Napoleon's cavalry ceased to exist from that point on, and still had not recovered in 1815 for the 100 Days' Campaign. The Russians reported burning the corpses of 123,382 horses as they cleaned up their countryside of the debris of war. Many, many others were eaten by the French for lack of food. Of the 66,345 men that had belonged to Davout's Ier Corps d'Armée in June 1812, there remained only 2,281. Of the glorious arsenal of near-2,000 French guns, 1,000 were captured; less than 400 artillery pieces were brought out of Russia. The 50,000-man Imperial Guard had been reduced to 500 men under arms and a further 800 sick, of whom 200 would never return to arms. The French also left behind thousands of their purpose-built military wagons and carts, a loss nearly as grievous as the horses which would cause massive supply problems for the coming two years. The French soldiers draped themselves in looted rugs, curtains and anything else they could find to keep warm; the elite French troops turned their bearskin shakos and buzbees into ear muffs. According to Carl von Clausewitz, "Besides himself, his principle generals and a couple thousand officers, he [Napoleon] brought away nothing of the whole army worth mentioning." Napoleon himself wrote in a letter: "I have no army any more! For many days I have been marching in the midst of a mob of disbanded, disorganized men who wander all over the countryside in search of food."