The desire to be in control and maintain authority is most pertinently displayed by the pigs through their actions. Once the Rebellion is successful, they easily take over the running of the farm. They are allowed to do so since they are the most intelligent. The other animals trust them and believe that their desire is to do everything in the best interests of all.
It soon becomes clear, though, that the other animals' interests are the least of the pigs' concern. This soon becomes apparent when the pigs claim the milk and apples for themselves. When a few grumble about the unfairness of it all, Squealer goes around to convince them otherwise:
"Comrades!" he cried. "You do not imagine, I hope, that we pigs are doing sin a spirit of selfishness and privilege? Many of us actually dislike milk and apples. I dislike them myself. Our sole object in taking these things is to preserve our health. Milk and apples (this has been proved by Science, comrades) contain substances absolutely necessary to the well-being of a pig. We pigs are brainworkers. The whole management and organisation of this farm depend on us. Day and night we are watching over your welfare. It is for YOUR sake that we drink that milk and eat those apples. Do you know what would happen if we pigs failed in our duty? Jones would come back! Yes, Jones would come back! Surely, comrades," cried Squealer almost pleadingly, skipping from side to side and whisking his tail, "surely there is no one among you who wants to see Jones come back?"
The extract clearly shows how easy it was for the pigs to manipulate and deceive the others. Since they are the cleverest, it stands to reason that they should be well-taken care of and secondly, the threat of Jones' return is a frightening thought. The animals are intimidated to accept what Squealer says as the truth, since they lack the intelligence to challenge him.
Because of their poor intellect, the other animals quickly forget how things really were in the past, thus giving the pigs even greater power. The pigs change history to suit their own ends. They slowly change the commandments to suit their lust for power and the luxury that comes with it. An example of this is the change of the maxims, 'Whatever goes upon two legs is an enemy' and 'Whatever goes upon four legs or has wings, is a friend' to firstly, 'Four legs good, two legs bad' and finally to, 'Four legs good, two legs better!' This happens after the pigs start walking on their hind legs. The most fundamental commandment: 'All animals are equal' is adjusted to later become the nonsensical, 'All animals are equal, but some animals are more equal than others.'
Once Napoleon banishes Snowball from the farm, he becomes more dictatorial. He calls himself 'Leader' and is constantly accompanied by his vicious guard dogs. Sunday Meetings are abolished and animals are brutally executed if they dare challenge his power or confess to having been secretly plotting with Snowball to take over the farm. The hens who for example, refuse to give up their eggs are starved.
Napoleon acted swiftly and ruthlessly. He ordered the hens' rations to be stopped, and decreed that any animal giving so much as a grain of corn to a hen should be punished by death. The dogs saw to it that these orders were carried out. For five days the hens held out, then they capitulated and went back to their nesting boxes. Nine hens had died in the meantime.
Four pigs are executed after confessing that they had been plotting with Snowball:
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.
When other animals confess, they are also ruthlessly executed. Napoleon's dictatorship has now developed into full-blown tyranny. No animal dared challenge his authority. He has now become almost god-like and should not be referred to as Napoleon any longer. He is 'Our Leader' now.
... 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
The ultimate display of the pigs' ruthlessness is displayed when Boxer falls ill and is sold to the knackers. The proceeds of this transaction is used to buy a case of whiskey for the pigs' enjoyment. Through his tyranny, Napoleon and his acolytes ensure that they remain in control, unchallenged. The pigs start trading with humans and adopt human traits: they live in the farmhouse, drink whiskey, smoke cigars, sleep in beds, wear clothes, carry whips and eventually:
No question, now, what had happened to the faces of the pigs. The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.