Austrian General Mack is defending Ulm from Napoleon's army. When the Prince of Liechtenstein arrives at Napoleon's headquarters to negotiate terms on Mack's behalf, Napoleon considers it to be a conspiracy on the part of the rulers of Europe and is intent on Mack's total surrender. The Russian army, led by Marshall Kutuzov, are called on by an Austrian emissary to provide support for Mack, but Mack surrenders before it is offered. Among the Russian troops are Nikolai Rostov and his squadron commander Denisov; both are desperate to see some action, but news arrives that they are to withdraw from the area. The French take Vienna and the Russian rearguard, under Prince Bagration, is charged with taking the full weight of their impending attack until the main force can get into position....

Napoleon sends General Savary to the Tsar to tell him how much his support of Austria wounds him, but also to learn Marshal Kutuzov's next move. Nikolai is reunited with Boris at his lodging, where they discuss the types of military career they seek. Prince Andre Bolkonsky arrives while Nikolai is relating his experiences at Schongraben. Nikolai is offensive to him about the worth of staff officers as they see no fighting. Savary reports back to Napoleon about the atmosphere of excitement at the Russian camp over what they see as their duty to half French ambitions. Kutuzov's army is camped on the Pratzen Heights and Napoleon hopes they can be drawn down to avoid attacking them there....

Pierre learns that Dolohov is Helene's lover and, at a banquet hosted by Count Rostov in Kutuzov's honor, he is deliberately provoked by his rival. When Dolohov announces aloud that after the banquet he has a date with a rich pretty married woman, Pierre finally loses control and challenges him to a duel. The duel takes place the next day and Pierre seriously wounds Dolohov. After Helene learns what has happened she asks Pierre for a separation, telling him that being his wife has been an embarrassment to her. Denisov, who has had his eye on Natasha, proposes marriage. She like Denisov but does not wish to marry him. A chance meeting at a post-house leads a desolate Pierre to a new way of life. Meanwhile at Tilsit, Napoleon and the Tsar prepare to sign a truce....

Leaving the Countess behind in Petersburg, the Count, Natasha and Sonya return to Moscow. Natasha's godmother, Maria Dmitrievna, is also staying with them. She informs Natasha that Andrei's father and sister are in Moscow and that she should call on them. The visit does not go well, primarily because the old Prince refuses to see anyone, causing both Princess Maria and Natasha to feel ill at ease. Natasha longs for Andrei to come back and weeps for him once she is home again. While enjoying various entertainments with her father and Sonya, Natasha meets Anatole Kuragin for the first time. As soon as the opportunity arises, he tells her that he has fallen in love with her. Reticent at first, Natasha soon succumbs to his charms....

Julia Karagina, who is now married to Boris Drubetskoy, pays a visit to the Rostovs and they discuss the prospect of leaving Moscow. Petya has joined a Cossack regiment but in line with the wishes of the Countess, Pierre transfers him to his own regiment which is training near Moscow. Pierre is unable to decide whether he should leave for Petersburg or stay in Moscow. Andrei meets Marshal Kutuzov again and tells him that his father is dead. Kutuzov believes that the forthcoming battle at Borodino will be pointless, as all that will change is that each side will lose some twenty thousand men. He also believes that the loss of Moscow is not important. Pierre meets up with Andrei at an encampment, but the battle begins before he has left the area....

The battle of Borodino is over, neither side having the energy to fight on. The loss of life has been as considerable as Kutuzov predicted. Pierre makes his way back to Moscow where he hears a proclamation stating that Moscow will be defended after all. Summoned to see Rostopchin, he learns that the speech was made in order to stem civilian panic and that the Governor is getting ready to leave. Rostopchin advises Pierre to leave the city, but he decides to remain in order to confront Napoleon, believing that their destinies are somehow inextricably linked - a view which he had derived from an interpretation of Revelation. Meanwhile, at the Rostov household, everyone is packing, when Natasha observes a seemingly endless line of Russian soldiers streaming out of the city....

Napoleon arrives in a deserted Moscow and is angered that there is no deputation of noblemen to meet him there. Pierre is still at his home, a fact which surprises his servant Gerasim, who warns his master that the streets are no longer safe. Pierre still believes that he is fated to murder Napoleon, but his musings over this ambition are interrupted by the arrival of a French officer called Ramballe. Pierre intercedes in an altercation between his drunk porter and Ramballe and the officer invites him to dine with him. They spend the evening getting drunk and exchanging confidences. Meanwhile, Napoleon learns from his generals of the presence of incendiaries in the city - who were instructed by Rostopchin before he left - and is concerned that if the city burns there will be no quarters for his troops....

At Yaroslavl, Natasha and Maria are still mourning the death of Andrei. Maria suggests that Natasha should come with her to Moscow, but she declines. When news reaches the Rostovs that Petya is dead, the Countess is inconsolable. Pierre returns to his house in Moscow and both Gerasim and Katishe are surprised to see him having thought he was dead Katishe tells him that Helene has died. Pierre attends a soiree given by the Drubetskoys and amazes everyone with his presence. Vasili Kuragin, who has now lost both of his children, is particularly moved by seeing him again. Pierre visits Maria Bolkonskya and is surprised to find Natasha there too. Natasha talks of Andrei for the first time since his death....