First published at the end of the Second World War, George Orwell's savage satire Animal Farm (1945) expressed his profound disillusionment with Soviet Communism, whose principles he had spent much of his career defending. It's an allegorical tale of the animals overthrowing their hated oppressor Farmer Jones and forming a socialist utopia - only to discover the hard way that, as Orwell so memorably put it, "some animals are more equal than others".
Events generally parallel those in early Soviet history, with Farmer Jones as Tsar Nicholas II, Old Major as Lenin (or possibly Marx), Snowball as Trotsky and Napoleon as Stalin, though they're sufficiently generalised to be applicable to almost any other totalitarian (not necessarily Communist) state with its five-year plans, forced industrialisation/collectivisation, show trials and revisionist speeches.
The film's credited producer is Louis de Rochemont, whose major achievement up to then was the creation of the March of Time newsreel format in the US, though he had also produced feature films dealing with sensitive political issues such as The House on 92nd Street (US, d. Henry Hathaway, 1945) and 13 Rue Madeleine (US, d. Hathaway, 1947). But later research suggests that the funding was provided directly by the CIA, who at the height of the McCarthy witch-hunts were keen to back a popular film with an explicitly anti-Communist message. To emphasise this, Orwell's profoundly pessimistic ending was softened, though it's still left ambiguous as to whether the rule of the hated pigs truly is coming to an end.
John Halas and Joy Batchelor were hired to direct what would turn out to be Britain's first animated feature film, with Maurice Denham supplying all the voices (bar the narration, by Gordon Heath). The visual style recalls the great Disney features of the 1930s and 1940s, though the content is far more adult and notably unsentimental: the animals more likely to react to major tragedies (most notably the horrific fate of their beloved companion Boxer) with resigned stoicism than righteous anger.
This, of course, is part of the point both the film and novel are making: that if you successfully delude the masses into believing that a perfect society is just around the corner, the masses will redouble their efforts to achieve it while conveniently turning a blind eye to the excesses of the ruling elite. If the style has dated somewhat, the content certainly hasn't.