In 1805 St. Petersburg, Pierre Bezukhov, illegitimate son of a rich nobleman, is introduced to high society. His friend, Prince Andrei Bolkonsky, joins the Imperial Russian Army as aide-de-camp of General Mikhail Kutuzov in the War of the Third Coalition against General Napoleon Bonaparte.

As 1809 nears its end, Natasha attends her first ball, where Andrei falls in love with her with the intent of marriage. However, as her father demands they wait, the prince travels abroad, leaving Natasha in desperate longing. But she meets Anatol Kuragin and forgets Andrei.

In 1812, as Napoleon's army invades Russia, Kutuzov asks Bolkonsky to join him as a staff officer, yet the prince requests a command in the field. Pierre sets out to watch the armies' impending confrontation. As the Battle of Borodino rages, he volunteers to assist in an artillery battery.

As Moscow is set ablaze by the retreating Russians, the Rostovs flee their estate, taking wounded soldiers with them, and unbeknownst to them, also Andrei. Pierre, dressed as a peasant, tries to assassinate Napoleon but is taken prisoner. As the French are forced to retreat, he's marched for months with the Grande Armée, until being freed by a raiding party.