The pigs who are always in confict are Snowball and Napoleon, who represent Trotsky and Stalin, respectively. "These two disagreed at every point where disagreement was possible" (19). Just as Leon Trotsky and Joseph Stalin engaged in a battle for power, eventually won by Stalin, the pigs vied for power and the Stalin representative (Napoleon) was victorious.
Stalin ultimately was victorious because he was a better stateman than Trotsky. He was able to appoint members to the ruling party of government. In a parallel fashion, Napoleon indoctrinated the sheep to chant at convenient times to overwhelm discussion. "It was noticed that they were especially liable to break into `Four legs good, two legs bad' at crucial moments in Snowball's speeches" (19). Ultimately it was Napoleon's "secret police" or the puppies taken from Jessie that chased Snowball from the farm.