The very first change that Napoleon introduces after Snowball's expulsion from the farm is to cancel the Sunday morning meetings ("They were unnecessary, he said, and wasted time") and to replace them with "a special committee of pigs, presided over by himself." One of the founding principles of Old Major's Animalism was that the animals should be equal, and that there should, therefore, be no hierarchies. By immediately replacing the communal meetings with the committee of pigs, Napoleon takes power from the other animals and concentrates it in the hands, or trotters, of the pigs.

The dogs that chase Snowball from the farm also, after that point, become a familiar feature of the farm. They are used by Napoleon to strike fear into and silence the animals:

Suddenly the dogs sitting round Napoleon let out deep, menacing growls, and the pigs fell silent.

The dogs are the novella's allegorical equivalent of Stalin's NKVD. Their role is to intimidate and suppress opposition.

Perhaps the most significant change to take place after Snowball's death is that the pigs gradually accumulate more and more power and become lazier while the other animals lose the democratic voice they once had and work harder and harder. The pigs take more and more for themselves and give less and less back to the other animals. In chapter six, for example, the pigs "suddenly moved into the farmhouse" and "slept in the beds." This signals that they are becoming just like the humans that they, most notably Snowball, fought so hard to replace at the beginning of the story, with this transformation reaching its climax at the end of the novella when the animals

looked from pig to man, and from man to pig, and from pig to man again; but . . . it was impossible to say which was which.

After Snowball leaves the farm—or, to be more precise, is forced to leave the farm—Napoleon and his propagandist-in-chief, Squealer, immediately set about trashing his reputation. Everything that subsequently goes wrong on the farm, such as the collapse of the windmill, is attributed to Snowball's malign influence. According to Squealer, Snowball keeps sneaking back to the farm in the dead of night to carry out acts of deliberate sabotage.

Squealer also tries to gaslight the other farm animals by casting doubt on their recollection of the Battle of the Cowshed. During this epic conflict, Snowball had taken the lead role, showing remarkable courage against their human oppressor. Now that he's persona non grata, Snowball's role in the battle is rewritten to make it seem that he was actually in cahoots with Mr. Jones all along, and that he has been tirelessly working ever since to destroy the revolution and restore human rule to the farm.

After Snowball leaves, the door for Napoleon to take over is wide open!  And so he does, proceeding to implement many changes on Animal Farm, including doing away with Sunday meetings, breaking more and more commandments, such as "No animal shall drink alcohol," and beginning to trade with humans to fund the windmill which he so adamantly opposed while Snowball was still on the farm, but quickly changes sides once Snowball has been exiled.