The dogs play an important role in the story. Napoleon secretly trains them from puppies to be obedient and loyal only to him. He first unleashes them to chase Snowball from the farm. Napoleon then uses fear of the dogs to impose a tyrannical rule. Squealer follows up with propaganda—the twisting of the truth—to justify this, saying there are enemies everywhere:
Discipline, comrades, iron discipline! That is the watchword for today. One false step, and our enemies would be upon us.
However, the dogs are primarily not tools of propaganda but of terror, the equivalent of Stalin's secret police. Their capacity for violence stamps out dissent.
Orwell shows how propaganda and terror work hand-in-hand to support a dictatorship when, after getting rid of Snowball, Napoleon decides to go ahead and build the windmill he had so vehemently opposed. Squealer assures the confused and disgruntled animals that this was his secret plan all along: Napoleon only pretended to oppose the windmill to outwit Snowball. Squealer then says:
"Tactics, comrades, tactics!" skipping round and whisking his tail with a merry laugh. The animals were not certain what the word meant, but Squealer spoke so persuasively, and the three dogs who happened to be with him growled so threateningly, that they accepted his explanation without further questions.
It is the presence of the dogs on one side, threatening violence, and Squealer's propaganda on the other, that allows Napoleon to do whatever he wants without facing protest.
In another instance, we see the dogs silencing any question of dissent as they accompany Squealer as he puts out more propaganda, this time to justify the pigs sleeping in beds, which was against the fourth commandment of Animalism until the pigs changed the rule:
Squealer, who happened to be passing at this moment, attended by two or three dogs, was able to put the whole matter in its proper perspective.