Quite crazy that between June 1812 (when Napoleon assembled the Grande Armée to invade Russia) and December 1812 when the army left, fewer than 50,000 of the assembled army of 600,000 remained to tell the tale?

In just over half a year, a rough winter, Russian rebellion and destruction of their own resources, starvation and disease cut the Grande Armée down to 1/12 of its original size.