So I've been thinking a lot about the invasion of Russia (and playing a lot of Napoleon: Total War) and I've been wondering: why invade Moscow? Wasnt St. Petersburg the actual capital of Russia at the time? Why not hug the coast, invading coastal cities, and then go for St. Pete?
To put it simply, Napoleon was after the Russian army, not any particular city, and the Russian army retreated towards Moscow, not St. Petersburg. If Napoleon had his way, neither city would have become involved in the campaign; he wanted to destroy the Russian army on the frontier, hundreds of miles from either city. For further detail, you may be interested in my previous posts on the campaign of 1812 in Russia here and here.