Another theme of Animal Farm is that power corrupts those who possess it. How does Orwell bring out this idea through the character of Napoleon?
As Napoleon amasses more power, largely unresisted, he becomes more egotistical. His corruption shows as he begins to demand being treated with adulation, which he calls "dignity." If at first the pigs used rational explanations for extra privileges, such as needing the apples for their brainwork, Napoleon nakedly sets himself apart out of the false belief he is superior to the other animals. We know however, that he is not. For example, he demonstrates he is not all that smart because he makes blunders, such as with the design for the windmill that collapses.
Nevertheless, he increasingly insists on being treated as special, styling himself a "Leader", and living in a house because it is better than "a mere sty:"
It was also more suited to the dignity of the Leader (for of late he had taken to speaking of Napoleon under the title of "Leader") to live in a house than in a mere sty.
Once you believe you are inherently better than those around you, you are traveling down the road to corruption. If you think you are superior, a lord of the universe, the ordinary rules obviously don't apply to you and can be disregarded. You are allowed to ruthlessly destroy your opponents, such as the hens who won't lay eggs properly.
This corruption spreads to having Squealer lie to tell a wholly false version of the Battle of the Cowshed that fashions Napoleon into a hero:
And do you not remember, too, that it was just at that moment, when panic was spreading and all seemed lost, that Comrade Napoleon sprang forward with a cry of 'Death to Humanity!' and sank his teeth in Jones's leg? Surely you remember that, comrades?" exclaimed Squealer.
Napoleon's corruption is complete when he has himself styled a virtual demigod, in the way of deluded dictators everywhere:
Napoleon was now never spoken of simply as "Napoleon." He was always referred to in formal style as "our Leader, Comrade Napoleon," and this pigs liked to invent for him such titles as Father of All Animals, Terror of Mankind, Protector of the Sheep−fold, Ducklings' Friend, and the like. In his speeches, Squealer would talk with the tears rolling down his cheeks of Napoleon's wisdom the goodness of his heart, and the deep love he bore to all animals everywhere, even and especially the unhappy animals who still lived in ignorance and slavery on other farms. It had become usual to give Napoleon the credit for every successful achievement and every stroke of good fortune.
The more brutally Napoleon leads the exploitation and pillaging of the other animals, the more grandiose the lies become. This is corruption at work.
The animals rebel and take over the farm. The original intent of this rebellion is to make the lives of the animals better. The goal is for the animals to control their modes and means of production. They will determine their own work schedules and they will reap all of the benefits of their work. This is basic communism and if practically and responsibly applied in this small community, the animals could/should be better off. In the beginning, their lives are better. However, like other historical examples of communism put into practice, their live gradually worsen and the leaders of the acquire too much power.
Napoleon is a representation of Joseph Stalin, a leader of the Russian Revolution and eventual leader of Russia. He, like Napoleon, increasingly gained more power and the people of Russia (like the animals of the farm) saw living conditions worsen.
Napoleon becomes more and more like a human. He distances himself from the other animals. This is contrary to Animalism (Communism). The original narrative of the rebellion is to show solidarity and unity among all animals, Napoleon included. But in his increasing desire for power, he clearly demonstrates that he (and some other pigs) require better nourishment and living conditions than the other animals. He raises and instructs nine puppies which will become his secret police, further isolating himself from the other animals. He ousts Snowball from the farm so he can have more power. At the end of Chapter VII, Napoleon has animals executed under the suspicion that they disagree with his policies or have rebellious thoughts. Napoleon also has Squealer occasionally change the tenets of Animalism to suit his growing greed. Each change signifies his increasing power and shows how the Animal Rebellion has gone further and further from its original intentions.
The corrupting influence of power on Napoleon is apparent from the earliest days of the Revolution. In Chapter Two, for example, the pigs become the "leaders" of the preparations for the Revolution because they are deemed to be the most intelligent animals on the farm. Once Jones is expelled from the farm, Napoleon becomes corrupted by the power that he holds. This is shown clearly when he steals the milk at the end of Chapter Two.
As the story progresses, power continues to corrupt Napoleon. In fact, he becomes so ambitious to be in total control of the farm that he expels Snowball because of his popularity among the other animals. The violent manner in which Napoleon expels Snowball shows that Napoleon will stop at nothing to have complete and absolute control over the farm.
From this point, Napoleon's corruption only increases. He breaks all of the Seven Commandments, rewrites them whenever he chooses, and uses violence and propaganda to quell any possibility of rebellion. In other words, he becomes even worse than Mr. Jones.