Animal Farm, by George Orwell (a British author) was published in 1945.  Orwell was a socialist, but had been distressed by NKVD activities he had experienced during the Spanish Civil War.  He wrote the book as a satire of totalitarian governments in general and an allegory of the Soviet Union in particular.

The human farmers represent the Russian monarchy and the capitalist countries that surrounded Russia and the USSR.  The animals represent different people and groups within the USSR.

The pigs represent different communist leaders:
    Old Major is a combination of Karl Marx, Vladimir Lenin, (and possibly Leon Trotsky)
        Napoleon represents Joseph Stalin.
        Snowball represents Leon Trotsky.
       Squealer represents the creators of Soviet propaganda, particularly the newspaper Pravda (meaning ‘Truth’) and its publisher (and later People’s Commisar for Foreign Affairs) Vyacheslav Molotov

The horses represent different roles,
    Boxer represents the working class, which works hard for the communist government and believes in it and its propaganda, but is exploited and abused by the leaders
    Mollie represents the upper middle class and lesser aristocracy, who only care about show and superficial things, and who fled Russia when things got bad

Benjamin (the donkey) represents the intellectuals of the USSR, who are exploited but cynically go along with things even though they understand that they are wrong.

Moses (the Raven) represents the Russian Orthodox Church

Jessie the dog represents others, such as artists, scientists, and athletes, who became critics of the USSR (and eventually defected to other countries)

The puppies represent the youth raised by the Communists to be so loyal to the government that they would turn against their own friends and family.  They are the secret police and security forces (Cheka and NKVD).

The sheep and the geese represent the masses who are deluded by the government and blindly follow its rules and fall for its tricks.