Aggressive dog training can be challenging at the best of times. It’s not the sort of thing to be taken lightly and perhaps should be undertaken by a professional dog trainer. If you are the dog’s owner, you may not like hearing it but your own behaviour could be one of the causes of the problem. If you leave your dog chained for long periods, tease your dog, under feed it or maybe even hit the dog as a punishment for bad act, then you are probably the cause of the dog’s aggressive behaviour.
Another possible reason could be that your dog has been attacked by other dogs or mistreated in some other way. Of course if you have only just got the dog and don’t know it’s history then you may never know why your dog is behaving this way.
Another reason behind aggressive behaviour could be an underlying medical condition. It is hard not to be irritable when in pain. A thorough exam by a veterinarian will most likely rule out any medical discomfort that may cause a dog to behave aggressively.