Orwell chose to portray the politicians involved in the Bolshevik Revolution and the beginning of communist Russia as pigs for several reasons. Similar to political leaders, pigs are known for their intelligence. Pigs are also known for their uncleanliness, which correlates with how power and wealth corrupt politicians. Moses, the raven, represents religious figures in the Russian Orthodox Church who were closely connected with the Russian monarchy. After the Bolsheviks declared religion and state separate for the first time in history, the religious leaders fled Russia. Joseph Stalin even persecuted religious officials and supported Karl Marx's ideology that religion is "the opiate of the masses." Orwell depicts this adverse relationship between the leaders of Russia and the religious officials in the form of the relationship between the pigs and Moses the raven. Interestingly, after The Battle of the Windmill, Moses returns and the pigs tolerate him as he spreads rumors of Sugarcandy Mountain. By allowing Moses to spread "false hope," Orwell portrays how religion pacifies the masses who are exploited by corrupt politicians.
In George Orwell's Animal Farm, the types of animals that are chosen to play particular characters are based on the traits that those animals embody. After the animals take over the farm, even though all the animals are supposed to be equal, a hierarchy develops and the pigs sit comfortably on top. The pigs Old Major, Napoleon, Snowball, and Squealer are intelligent animals who provide guidance (albeit different types of "guidance") to the animals on the farm. Pigs are known to be intelligent farm animals, so Orwell exploits this trait when he personifies the pigs in Animal Farm. Similarly, Moses the raven is a preacher in the story and delivers sermons to the other animals on the farm. He represents religion, and the other animals are placated by his words. Ravens are known for their croaking voices, so again this trait is exploited in the novel.