Orwell wrote Animal Farm in order to describe the process of corruption in revolution, specially the Russian Revolution.
Orwell’s books expose the dark side of the human condition. He wrote Animal Farm because he wanted to create an allegory, or fable, of the Russian Revolution. He based all of the characters and the events on what actually happened. Therefore, he strongly was convinced that the Russian Revolution was a force of corruption, because that is what he presents of the revolution in Animal Farm.
Using allegory … Orwell made his political statement in a twentieth-century fable that could be read as an entertaining story about animals or, on a deeper level, a savage attack on the misuse of political power. (enotes introduction)
Although Orwell wanted people to realize the abuses that came with the Russian Revolution and the Soviet Union, he also wanted to get people thinking about the nature of revolution in general. Animal Farm’s ending describes how he felt about revolution.
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. (ch 10)
The pigs promised a better life for the animals, but they abused them and used them just as much as the humans did. In the end, they cannot tell the difference between the humans and the animals. The animals are so corrupt they have basically become human.
Another famous line captures the key to the book and Orwell's beliefs.
There was nothing there now except a single
Commandment. It ran:
ALL ANIMALS ARE EQUAL
BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS (ch 10)
With this comandment the pigs are able to take over the farm. Orwell wanted people to realize that the Soviets were doing the same thing.
Orwell intentionally wrote his book in simple, easy-to-translate language.
"I thought of exposing the Soviet myth in a story that could be easily understood by almost anyone and which could be easily translated into other languages." (enotes historical background)
Orwell wanted to be sure that no one bought the lies. He was not convinced that the Soviets were telling the truth, and he told the story in such a way that it was obvious who was Stalin, Trotsky, and Hitler. He was writing because he was fed up.
Orwell is trying to make the point that the vision of an idealistic society cannot translate into reality, that political and social revolutions seldom, if ever, manage to hold to their original purity of purpose. The original aim of Animal Farm, after the euphoria of the victory against the common enemy, Man, is for all the animals to work together for the common good, to create a community where there is true freedom and equality for all, and where the strong protect the weak. However, this soon degenerates into disagreements and power struggles and leads to oppressive rule by a tiny minority. In fact, the majority of the animals find that they have simply exchanged one oppressive government (the humans) for another (the pigs). Most ironically, the pigs actually end up joining forces with humans once again. Orwell based this fable on events in Russia in the first half of the twentieth century, where an idealistic communist revolution led first to brutal civil war and then eventually, a grim totalitarian state under Josef Stalin. However Orwell's point about the nature of revolutions and the corrupting effects of power can be applied universally.