In Chapter 7 of Animal Farm, the harsh winter has caused the farm to be less productive. As a result, Napoleon starts to make deals with the other farmers, requiring an increase in production of the animals. When they protest, he uses intimidation, starvation, and fear tactics to get his way, and then uses his trained dogs to force "confessions" out of innocent animals:
When they had finished their confession, the dogs promptly tore their throats out, and in a terrible voice Napoleon demanded whether any other animal had anything to confess.
(Orwell, Animal Farm, george-orwell.org)
By creating a common enemy in Snowball, said to be sneaking onto the farm and sabotaging it, Napoleon is able to seed dissension and paranoia in the animals. By executing animals who confess -- even when the confession is forced -- he shows that any stance against his rule will not be tolerated. Napoleon becomes a dictator, censoring and exploiting the animals to keep them in submission.