A large proportion of dog-on-dog aggression starts as fear or nervous aggression rather than genuine hostility. When early signs go unrecognised or are handled in ways that unintentionally reinforce the fear, a nervous puppy can develop into an adult dog showing real aggression. Fear aggression in puppies typically involves growling or snapping to make scary situations go away. Comforting heavily during fearful reactions or avoiding other dogs can reinforce the fear and remove needed socialisation. The cycle strengthens as the puppy learns that aggressive behaviour causes threats to retreat. Early recognition and gradual, well-managed exposure can break the pattern and build genuine confidence.