How is George Orwell's Animal Farm an example of an allegorical story?

George Orwell's novella Animal Farm is considered an allegorical tale because all of the characters and events in the story symbolically represent various people, places, and events that correspond to the Russian Revolution of 1917 and the early years of the Soviet Union under the leadership of Josef Stalin. Old Major symbolically represents Karl Marx or Vladimir Lenin and the school of thought known as Animalism represents Communism. Snowball represents Leon Trotsky, while Napoleon's character represents Josef Stalin. At the beginning of the story, Mr. Jones is expelled from his farm, which symbolically represents the initial Russian Revolution when Tsar Nicholas II was forced to abdicate. The Battle of the Cowshed represents the infighting during the Russian Civil War of 1917–1922, and the Battle of the Windmill allegorically represents the Battle of Stalingrad.
Other characters in the novella allegorically symbolize groups and aspects of the early Soviet Union. Boxer represents the proletariat workers, while Squealer stands for Stalin's propaganda machine. Molly symbolizes the bourgeoisie, the nine ferocious dogs represent Stalin's secret police force, and Moses allegorically represents the Russian Orthodox church. Overall, Orwell's Animal Farm is an allegorical tale that tells the story of the 1917 Russian Revolution and the early years of the Soviet Union.