Old Major, the old boar on the Manor Farm, calls the animals on the farm for a meeting, where he compares the humans to parasites and teaches the animals a revolutionary song, 'Beasts of England'. When Major dies, two young pigs, Snowball and Napoleon, assume command and consider it a duty to prepare for the Rebellion. The animals revolt and drive the drunken and irresponsible Mr Jones from the farm, renaming it "Animal Farm". They adopt Seven Commandments of Animalism, the most important of which is, "All animals are equal".
Snowball attempts to teach the animals reading and writing; food is plentiful, and the farm runs smoothly. The pigs elevate themselves to positions of leadership and set aside special food items, ostensibly for their personal health. Napoleon takes the pups from the farm dogs and trains them privately. Napoleon and Snowball struggle for leadership. When Snowball announces his plans to build a windmill, Napoleon has his dogs chase Snowball away and declares himself leader. Napoleon's rule
Napoleon enacts changes to the governance structure of the farm, replacing meetings with a committee of pigs, who will run the farm. Using a young pig named Squealer as a "mouthpiece", Napoleon claims credit for the windmill idea. The animals work harder with the promise of easier lives with the windmill. After a violent storm, the animals find the windmill annihilated. Napoleon and Squealer convince the animals that Snowball destroyed it, although the scorn of the neighbouring farmers suggests that its walls were too thin.
Once Snowball becomes a scapegoat, Napoleon begins purging the farm with his dogs, killing animals he accuses of consorting with his old rival. He and the pigs abuse their power, imposing more control while reserving privileges for themselves and rewriting history, villainising Snowball and glorifying Napoleon. Squealer justifies every statement Napoleon makes, even the pigs' alteration of the Seven Commandments...