This part begins to sag as Tolstoy indulges in philosophizing. Why does it sag? For me, John Gardner's concept of the novel as a continuous "vivid dream," is key to explaining that. (The author of several novels, Gardner is best known for his beloved if controversial The Art of Fiction. Read his Paris Review interview here.
So, following Gardner's very commonsensical point, to hold our attention, a novel needs to be not only vivid, but continuous. There are so many novels to read that even in a fairly high level workshop I find that there several participants who haven't read thus-and-such a classic (and speaking of which, here I am reading War and Peace for the first time!) so I use the analogy of popular movies. Let's say you're watching Gone with the Wind. Would it really work if, right in the middle (oh, I don't know, the burning of Atlanta?), the camera swung around to show Clark Gable in the makeup chair, taking a phone call from his agent? Neither would we want to see the caterer's folding table spread of cheese cubes and Diet Coke, anywhere in the midst of Gladiator's ancient Rome. (No, we don't want to see Russell Crowe in the makeup chair, either!) So, in interrupting the "vivid dream" with all this professorial blather, Tolstoy slows down, ayy, gums up the whole show. That said, the show is still going at 100 mph. I'm loving this book, feeling so grateful, thrilled in fact-- it's a whole world opened up to me.
For Americans of my generation (second half of 20th century) the mesmerizing glamour of Napoleon is difficult to understand; Tolstoy shows it spendidly, e.g.
.. Hundreds of uhlans followed [the adjutant into the river]. It was cold and scary in the middle and in the swift current. The uhlans grasped at each other, fell off their horses, some horses drowned, men drowned as well, others tried to swim for it, some in the saddle, others holding onto their horses' manes. They tried to swim forward to the other side, and, though there was a ford a quarter of a mile away, they were proud to swim and drown in this river before the eyes of a man who sat on a log and was not even looking at what they were doing. When the adjutant returned and, choosing the right moment, allowed himself to draw the emperor's attention to the devotion of the Poles to his person, the little man in the gray frock coat stood up and, summoning Berthier to him, began pacing up and down the bank with him, giving him orders and occasionally plancing with displeasure at the drowning uhlans, who distracted his attention.
I was also struck by the narrative's juxtaposition of Anatole's going after Natasha and Napoleon's invading Russia. (Oh, there are about 11 PhD theses on all these interrelated and juxtaposed plots and subplots...)