When Napoleon seizes the nine dogs for himself, it's one of the early signs of his corrupt intentions. He takes them from their parents, Jessie and Bluebell, shortly after they are born, “saying that he would make himself responsible for their education,” and then raising them in isolation from the rest of the farm (3.12).
The dogs do not reappear until tension between Napoleon and Snowball reaches a breaking point. After it appears that Snowball has won the crowd, Napoleon lets out a whistle; “At this there was a terrible baying sound outside, and nine enormous dogs, wearing brass-studded collars came bounding into the barn” (5.14). They drive Snowball off the farm. From this point on, the dogs are constantly with the pigs, intimidating and threatening the other animals to make sure that the pigs get their way. The narrator ironically notes, “It was noticed that they wagged their tails to him [Napoleon] in the same way as the other dogs had been used to do to Mr. Jones” (5.15). The end of the novel is already being foreshadowed; the pigs are becoming like their human predecessors.
The dogs essentially become the pigs’ partners in crime. They are the ones who carry out Napoleon’s execution orders, and they growl at anyone who seems to question the pigs’ decisions. In exchange, the pigs let them stay in the farmhouse, and feed them better than the other animals.
The dogs are a direct allusion to the NKVD, Stalin’s secret police force. The NKVD came to have an enormous role in Soviet life in the 1930s and 1940s. They proved their reach in 1940 when Trotsky (a.k.a. Snowball) was assassinated in Mexico by Ramón Mercado, a NKVD agent. During the "purges," the secret police helped Stalin round up all those members of Soviet society that were perceived as a threat, and the NKVD participated in their exiles and executions. In short, the secret police, like the nine dogs, was the violent force that allowed Stalin to remain in power. (To learn more about Stalin's "purges" and the assassination of Leon Trotsky, see "Symbols, Imagery, Allegory.")The nine dogs Timeline