Volume III, Book I, Chapter III

Meanwhile, back in Poland, waiting for things to happen, the sovereign is being feted by Count Benningsen in the Vilna province. He's been in Poland for a while.  Funny that the last soldiers who through themselves in the river for Napoleon were Polish, too.  Hmmm.

Anyhow, here we are at a ball in Vilna.  Boris shows up, without his wife, and dances with Helene, who naturally is there - all the aristocrats follow the tsar. Boris is up to his old tricks - he has money now because of his wife but still wants to be in the right circles.

The sovereign is pulled over by Balashev, who whispers something in his ear. Alexander grabs his shoulder and walks quickly across the room. Boris is nearby, and overhears him say that he will not make peace as long as there is one armed Frenchman in his country.  He's not happy to have had Boris overhear that Russia has been invaded without the declaration of war that they've all been waiting for, but Boris sure is. He has special information now that will make people think he's privy to things he's actually not. 

The sovereign writes Napoleon a letter apologizing for some incident about passports (I'm so much more interested in the people I just glide over some of these things),  but does not mention the phrase he came up with about not having peace while there is a single armed man on Russian soil.

I read a little on Wikipedia the economic reasons which aren't mentioned in the novel so far, either because in 1865 they weren't as clear, or because this novel is inherently on Russia's side (which makes sense), but it's interesting to note that Russia had annexed Poland, and France's invasion was ostensibly to free Poland, but Russia depended on France for manufacturing, since it was rich in natural resources, but not factories.  I'm not reading much on the history, only because I don't want to know what happens, and this book is mentioned everywhere with this war, so spoilers abound.  Anyhow, interesting actual historical context.

I aslo love Boris in there, in that actual historical event, like a cartoon character against a film.   It's brilliant how Tolstoy creates these characters and has them witness historical events. Not only do we see the Tsar's reaction to the invasion as its happening, but get this great sense of Boris' sliminess at the same time.  It's brilliant.