To reduce barrier aggression in dogs, you can follow a behavior modification training regime to help improve impulse control and curb aggression. If you are struggling to train an aggressive dog, you can also seek help from a certified professional dog trainer. Prepare a reward, choose a high-value treat that your dog loves, as treats are a powerful dog training tool and serve as positive reinforcements. Go to a private fenced area, choose a location where you and your dog are alone, and your pet can safely be off-leash. Provide a treat, begin by giving your dog a treat regardless of their behavior, provide them with two or three treats, so they understand you have something they want. Wait for your dog to remain calm, wait and watch your dog to see if they remain calm, if they are calm after five seconds, give them a treat, if they act aggressively, turn and walk away. Repeat this multiple times, gradually increasing the amount of time you require them to remain calm.