In 1805, most of Europe is torn apart by Napoleon Bonaparte’s drive to conquer more and more territory.  In Moscow, many young men have joined the army, including Nicholas Rostov, the son of Count Ilya Rostov and his wife Nataly, and the brother of young Petya and the flighty but devoted Natasha.  The Rostovs’ friend Pierre, the illegitimate son of the ailing, wealthy Count Bezukhov, has recently returned from Paris and believes that Napoleon is a "cleansing force" who can establish equality and liberty.

Despite his pacifism, Pierre wishes Nicholas well and then visits his friend, army officer Dolokhov, a notorious rake.  There, the comrades indulge in drinking games but are interrupted by Prince Andrey Bolkonsky, an officer of much finer character than Dolokhov.  Andrey informs Pierre that his estranged father, who is near death, is calling for him, and Pierre goes to his father’s mansion, where various relatives snub him.  Their derision changes to hypocritical concern, however, after the old count dies and it is discovered that he has accepted Pierre as legitimate and named him his sole heir.  The scheming Helene Kuragina immediately sets her sights on Pierre and soon he falls in love with her, while her father, Prince Vasili Kuragin, insinuates himself as the administrator of Pierre’s vast estates.

One day, Pierre runs into Andrey in the country as Andrey is escorting his pregnant wife Lise to his father’s house.  Andrey, who feels trapped by the clinging Lise, had earlier advised Pierre never to marry, and now Pierre refuses to accept his warnings.  After Andrey takes Lise to live with his sister Mary and gruff father, Prince Nicholas Bolkonsky, he leaves for the front and is made an adjutant to the commander of the army, Gen. Mikhail Kutuzov.

Later, at the Battle of Austerlitz, Andrey attempts to rally the retreating men by grabbing their banner and rushing the enemy, but he is wounded and left for dead.  While surveying the battlefield, Napoleon comes across Andrey and, admiring his courage, orders that he be tended to by his personal physician.  In Moscow, when Pierre learns that the Russians are suing for peace, Helene persuades him to return to the country alone so that she can spend the season in the city, welcoming the soldiers.  Nicholas comes home safely, much to the delight of Natasha.

Meanwhile, Andrey returns to his family, just as Lise goes into labor.  Although their son Kolya survives, Lise dies after giving birth, and the grieving Andrey blames himself for not offering her enough comfort and love.

As time passes, Helene begins a flirtation with Dolokhov, and when Pierre learns of the rumors about them, he insults Dolokhov and accepts his challenge of a duel.  Although Pierre is woefully unskilled with firearms, he manages to shoot and wound Dolokhov, while the soldier’s shot goes wide and Pierre is unharmed.  Infuriated that he was provoked into acting in such an uncivilized manner, Pierre separates from Helene and agrees to accompany the Rostovs to their country estate.

One day, while they are hunting, they meet Andrey, who is enchanted by Natasha.  Later, Andrey dances with Natasha when she attends her first ball and realizes that he wants to marry her.  Prince Bolkonsky urges Andrey to wait a year, as Natasha is so young and the Rostovs are not their social equals, but promises to consent if Andrey still wishes to marry her then.  With Natasha’s promise to wait for him, Andrey then joins the mission to Prussia, where Czar Alexander and Napoleon sign a peace treaty in June 1807.

While Andrey is gone, however, Natasha is seduced by Anatole Kuragin, Helene’s brother, who is as cold-hearted and debauched as his sister.  Even though he is secretly married, Anatole persuades Natasha to elope with him, but their plans are foiled by Natasha’s cousin Sonya and Pierre, who threatens Anatole with exposure of his marriage if he ruins Natasha’s reputation.  Pierre’s threats come too late, however, and soon all of Moscow is gossiping about Natasha, who falls ill after Andrey ends their relationship.

After several months, she begs Pierre to convey her regret to Andrey, and Pierre, who is in love with her, assures her that she is blameless, and that if he were free, he would ask for her hand.  Later, in 1812, Napoleon crosses the River Niemen into Russia, despite the peace treaty.  Faced with the superiority of the French Army, Kutuzov orders his men to retreat, and as they fall back, the soldiers and peasants set fire to the countryside so that the French will be without provisions.  Although his officers protest his strategy, Kutuzov insists that the only way to save Russia is by letting the French wear themselves out.  Soon the city of Smolensk is abandoned and Kutuzov decides to make a stand at Borodino.

Determined to see war firsthand, to decide if his hatred of it is valid, Pierre travels to Borodino, where he finds Andrey’s camp on the eve of the battle.  Although Pierre urges Andrey to forgive Natasha, Andrey states that he cannot.  The next morning, Pierre watches with mounting horror as the fighting rages around him and the French slaughter the Russians.  Finally realizing that his hero is just a tyrant, Pierre damns Napoleon. Kutuzov then decides to fall back beyond Moscow, leaving the ancient capital city to the French.

In Moscow, the Rostovs are among the many families preparing to flee when some wounded Russian soldiers arrive, hoping to be billeted at their home after their departure.  Natasha insists that the men cannot be left behind to be captured, however, and they are loaded into the Rostov wagons and taken to a distant village.  In Moscow, Napoleon is infuriated to learn that the government has fled, leaving no one behind to surrender to him.  Although Pierre lies in wait one day, hoping to assassinate the French emperor, he cannot do it and is taken prisoner.

Meanwhile, Natasha has learned that Andrey is among the wounded in their care and reunites with him.  While Pierre is befriended by a fellow prisoner, the peasant Platon, the Rostovs take Andrey to a monastery to convalesce.  Andrey’s wounds prove fatal, however, and he dies just after Mary and Kolya arrive to bid him farewell.

In Moscow, Napoleon realizes that he has been outmaneuvered by Kutuzov, and, fearing being trapped in Russia during the winter, orders his men to retreat.  The prisoners, including Pierre and Platon, are forced to accompany the soldiers during their 2,000-mile march, and many of them die.  The Russian soldiers follow behind the French, allowing them little rest and picking off stragglers.  Petya, who has joined the army against his parents’ wishes, is sent with a dispatch to Dolokhov, ordering his platoon to join the main regiment.  Eager for one last fight, Dolokhov insists on attacking the French the next morning and allows Petya to accompany him. Petya is killed during the engagement, and although Pierre is freed, he is too overcome by the boy’s death to rejoice.  Dolokhov informs Pierre that Helene has died, and later, joins the other Russian soldiers as they attack the French, who are fleeing back across the Niemen.

Later, the Rostovs return to Moscow and find their mansion a burned-out shell, with only one wing remaining intact.  Natasha rallies her family to make the best of what they have, however, and as the others settle in, Natasha sadly remembers happier times.  She then sees Pierre in the doorway and rushes to embrace him.  Telling him that he is like their house, which suffers and shows its wounds but still stands, Natasha kisses Pierre, and they walk together in the garden.