Animal Farm was written by George Orwell and published in 1945. This novel is an allegory - even though it is set on a farm and stars a cast of farm animals, it reflects the events of the Russian revolution of 1917.
The animals are all clever representations of Russian politicians, voters and workers. Orwell used the novel to make his opinions on Russian leaders heard.https://www.bbc.co.uk/bitesize/guides/zccjfrd/revision/1
Social and Historical context
Though Animal Farm enacts the events of the Russian Revolution, Orwell was prompted to write and publish Animal Farm in response to concerns he had about censorship within the British media during the 1940s. Though critical of Lenin and Stalin in the 1920s and 1930s, Great Britain allied with Stalin’s Soviet Union in the latter half of World War II. To garner public support for this alliance, the media began to censor anti-Stalin and anti-Soviet publications. In his proposed preface to Animal Farm, Orwell describes the British press as
“extremely centralized, and most of it is owned by wealthy men who have every motive to be dishonest on certain important topics . . . At this moment what is demanded by the prevailing orthodoxy is an uncritical admiration of Soviet Russia.”
https://www.enotes.com/topics/animal-farm/teaching-guide/historical-context
Because Animal Farm is so critical of Soviet Communism, some readers may be surprised to learn that Orwell was a committed socialist. As a result of his experiences as a colonial policeman in Burma and while living in working-class areas of London and Paris, Orwell became a fierce opponent of colonialism and unchecked capitalism. Eventually he joined the Socialist Independent Labor Party, and he documented the development of his political beliefs in a series of essays and books, most famously The Road ToWigan Pier (1937).
https://www.sparknotes.com/lit/animalfarm/context/historical/orwells-politics/
The revision began almost immediately. Frances Stonor Saunders, in her fascinating study "The Cultural Cold War," reports that right after Orwell's death the C.I.A. (Howard Hunt was the agent on the case) secretly bought the film rights to "Animal Farm" from his widow, Sonia, and had an animated-film version produced in England, which it distributed throughout the world. The book's final scene, in which the pigs (the Bolsheviks, in Orwell's allegory) can no longer be distinguished from the animals' previous exploiters, the humans (the capitalists), was omitted. A new ending was provided, in which the animals storm the farmhouse where the pigs have moved and liberate themselves all over again. The great enemy of propaganda was subjected, after his death, to the deceptions and evasions of propaganda—and by the very people, American Cold Warriors, who would canonize him as the great enemy of propaganda.
https://www.newyorker.com/magazine/2003/01/27/honest-decent-wrong