The saga begins in Russia in 1805. When Pierre (Paul Dano), Natasha (Lily James) and Andrei (James Norton) are first introduced to viewers, their youthful ambition, despite their privileged circumstances, is to find meaning in their lives. Kind-hearted but awkward Pierre, the illegitimate son of Russia's richest man, wants to change the world for the better. The spirited Natasha is searching for true love, while handsome and gallant Andrei (James Norton), frustrated with the superficiality of society, seeks a higher purpose.
At the same time, Napoleon's army edges ever closer to Russia's borders. As everything they thought they knew is thrown into question, Pierre, Andrei and Natasha find themselves in a time when Russian lives are about to change forever.
Natasha's older brother Nikolai (Jack Lowden) joins the army immediately and matures during the course of the wars with Napoleon. Like Pierre, Natasha, and Andrei, he also experiences romantic vicissitudes: despite his childhood love for his cousin Sonya (Aisling Loftus), his impoverished parents insist instead that he marry a rich bride like the superficial Julie Karagina or the religious Marya Bolkonskaya (Jessie Buckley).
Having begun with Napoleon's conflict with Russia in 1805, the story concludes in 1812 after Napoleon has been driven from Russian soil following his invasion of the country. All of the central families of the saga have undergone major changes and lost members, but those remaining have experienced a transformation and a new life, with new growth and new families started.