Lots of new guys get appointed to high positions in the Russian army. Mostly there’s just in-fighting and politics and general backstabbiness. Which is fine, according to Tolstoy, since none of these men have anything to do with anything anyway.
Meanwhile, Emperor Alexander writes Kutuzov a letter asking why the army isn't attacking the French. He's a little grumpy.
But by the time this letter arrives, there’s already been a battle between the two armies – mostly because Kutuzov can’t hold anyone off anymore.
Basically, a Russian soldier who’s out on patrol at Tarutino just happens to run into the left flank of General Murat’s forces. He comes back, the story gets up to the highest ranks, and from then on it’s a foregone conclusion that they'll fight.