Napoleon's most concrete instrument of control is the nine dogs he raises in secret. They appear at the meeting where Snowball is expelled, chasing him off the farm, and their presence in Napoleon's household from that point forward is a constant deterrent to dissent. The dogs are not used constantly. In most scenes they are simply present or implied. But their existence is enough. When Squealer gives an explanation that does not add up, and the animals begin to look uncomfortable, a dog's growl is enough to settle the room. The potential for violence disciplines behaviour far more efficiently than the exercise of it would. Orwell also shows how fear operates in more subtle ways. The public confessions and executions that occur mid-way through the book are among the most horrifying scenes. Animals confess to crimes they clearly did not commit, crimes linked to Snowball or to Jones, and are immediately killed by the dogs. Other animals watch. The psychological effect is not just fear of execution. It is the demonstration that truth has no protective power. Being innocent is not enough. Anyone can be accused and anyone can be killed. The only safety is silence and compliance. The animals' response to the executions is telling. They are terrified and distressed. But they do not revolt. They huddle together and try to understand what has happened. Eventually they conclude it must have been their own fault, some failure of loyalty or dedication. The self-blame is the propaganda working at its deepest level: making the victims responsible for their own oppression. Orwell's argument is that systematic fear creates a form of psychological oppression that survives long after the overt violence has passed.