Napoleon, Snowball and Squealer are the three pigs who organize the thoughts proclaimed by Old Major into the principles of Animalism.
Soon after the revolt, Napoleon takes the nine puppies from their mother and trains them to be his body guards and secret police force. Napoleon runs Snowball off the farm and begins to take total leadership and control over all the other animals. He becomes a dictator and orders the deaths of any animals who confessed to be allies with Snowball.
Napoleon negotiates with Jones's neighbors. "Like Joseph Stalin, the Soviet leader who had negotiated with England while making a secret deal with Hitler, Napoleon negotiates with one of Jones's neighbors, Mr. Pilkington, while making a secret agreement with Mr. Frederick, another one of Jones's neighbors."
In the end, he breaks the principles of Animalism and begins to walk upright like the humans he had denounced.
Orwell describes Snowball as "quicker in speech and more inventive" than Napoleon. Snowball organizes the animals into committees. He created the military strategy known as Battle of the Cowshed. This battle was "a defense of the farm against the humans which proves useful when Jones and his friends try to retake the farm. Snowball shows his expert use of military strategy during the attack—which becomes known as the Battle of the Cowshed—and is later awarded a medal."
Snowball comes up with the idea of the windmill to produce electricity. Of course, Napoleon later steals his idea and takes all the credit for such an idea. Snowball represents the historical figure of Leon Trotsky:
Like Trotsky, who was exiled from Russia by his former partner Stalin, Snowball is eventually run off the farm by Napoleon.
After Snowball is gone, Napoleon blames everything on Snowball.
Squealer is a smooth talker. He has an answer for everything. He explains things to put Napoleon in a good light. Squealer is the propaganda chief for the pigs. He explains why the commandments seem to be changing. He tries to explain why the ambulance that takes Boxer away has a sign on it that says horse slaughterer. He is so fat by the end until his eyes are like slits. He has become a selfish, greedy pig like Napoleon by the end of the story.