Begun with over 600,000 French and allied troops - ended with 27,000
This article originally appeared at South Front
A short and excellent overview of Napoleon's invasion of Russia in 1812 that led to his downfall as the master of Europe as the war he started finished with Russians entering Paris in 1814 and removing him from power:
If your appetites have been wheted do watch this lecture by the excellent historian of Russia Dominic Lieven where he presents the arguments from his extraordinary book Russia Against Napoleon: 1807-1814:
Lieven's key point is that Russia's role in ending Napoleon's reign is downplayed including in Russia itself.
Finally, take a note of the following chart:
It shows how many troops Napoleon had at his disposal in the various stages of his advance and retreat. You can see that most of Napoleon's losses ocurred during the advance into Russia - that is to say in the summer. By the time he reached Moscow - which was on September 14th - he was already down to just 100,000 men - a small fraction of what he had started with. Thus it is erronous to say winter was the key factor of Napoleon's defeat.