Canine aggression, while an unpopular topic, is one that truly needs attention. Owners of aggressive dogs are often afraid to seek help, for fear that the dog will be taken away, or that they will be ridiculed or  judged "incompetent". Owners of "unpopular" breeds also may not want to tarnish their breed's reputation further. However, dominant dogs exist in dogs across the board, reagrdless of breed...and failing to deal with the issues at the first sign of trouble simply creates a dog who may go on to actually hurt someone! Viewed objectively, dominance problems are like any other problem: housebreaking, leash training, teaching your dog to come; however, dominance/aggression has a terrible stigma, because even though it comes as naturally to the dog as barking, digging, and tugging on the the human world, a dominant dog is a potentially dangerous dog.

First and foremost~  The best advice anyone can give on canine dominance and aggression, is to let a qualified trainer or behaviourist evaluate your animal in person. Aggression is a serious matter than can escalate quickly, and it is easy for an owner to mistake their animal's intentions, or miss a subtle cue in behaviour or body language that (if taken into consideration) changes the whole picture. Frequently, dominance is mistaken for viciousness...puppy mouthing mistaken for an attack...fearful reactions taken as aggressiveness. You don't want to treat a fearful dog as you would a dominant/aggressive one, so you do need to be sure of what is really happening before acting on it. Trying to understand what is going on in the dog's mind is paramount, since a lot of things that are normal and natural behaviour--to a dog--are serious problems when humans are involved.
UNDERSTANDING CANINE BODY LANGUAGE IS ABSOLUTELY CRITICAL to the human/dog relationship! Please, please learn to "read" your dog. Go HERE for some great dog links, including body language.

Additionally, be aware that, in an intense dominance conflict, your dog may suddenly switch from dominant aggression, to
DEFENSIVE or fearful aggression! He may be frightened or taken aback by your reaction, rethink his stance, decide that pushing you so far was a bad idea...and go into defense mode. Physical corrections and rough handling at this point may actually force him to act more aggressively, and make things worse. Keep a close eye on his body language, and leave him the option to back out gracefully if he has overstepped his bounds.

It's also extremely important to keep in mind that
the way a DOG views the world, and its relationships with others,  is quite different from the way a human does.  Our family structure promotes equality...dogs' family structure revolves around rank & protocol. Two very different views; the dog cannot change his/her view. WE must change ours,  if we are to live in harmony.
A good example of problems caused by this difference in mentality between humans and dogs would be this scenario, which happened at my buddy's house recently: He has an older female labrador, who's been alpha bitch since, well, always. He also has a young female rottweiler, who is just now "coming of age". The rott is a dominant, alpha-type animal...and is easily twice the lab's size. The lab just went into heat...and the rott girl decided: now is the time to stage a coup, and take her rightful place as alpha female. This fellow has teenage daughters, who are very upset by the fact that the dogs are now fighting. They're mad at the rott, for "being mean to the lab all of a sudden". So, they feel sorry for the lab, & heap her with special attention & try to make her feel better, because "the rottie is picking on her". EXACTLY the wrong thing to do...if these two dogs are *ever* going to live in harmony again, the humans need to recognize that the alpha spot belongs to the rott. AND, all human members of the family, anthropomorphizing aside, need to learn to respect that law and to treat the rott according to her personality and her pack rank. "Not fair!" you may be thinking..."what if I'm closer with the lab and want to give her the extra privileges? What if the rottie takes the lab's favourite stuffy? Why should the rott get special treatment?" Now you're thinking like a human--but the dogs are still thinking like dogs...and if you ignore their rules, they'll have to fight again and again because since YOU haven't accepted their decision, they still have something to prove.
Another example of this mentality backfiring would be preparing the dog's food before your own. Your view: it's a sweet gesture of love and appreciation...putting the needs of someone you care about before your own. The dog's view: you are saying "You, Prince, are top dog around here. Eat as much as you care to, and I'll have some after you've finished." It is just one of the many ways that we humans can portay ourselves as an underling without even noticing it. (For the record, it's fine to feed dogs from the table...but it is important to feed them
after all human family members have finished.) Prince is sitting there thinking one of two things: "Man, is this lady a pushover! I could knock her out of rank, easy..." or "ummm....well....Who do I look to for direction? That two legger's not the alpha...she's lower in rank than me...but there HAS to be a leader...I've got it! I'll be the leader!" Dogs in general don't cope well with ambiguity--and they will feel uneasy, anxious, and confused until the structure is clear to  them. (How do YOU feel when you have a problem you don't know how to solve? To a dog, not knowing where he stands in life is a problem with a capital "P"!) Somebody must be in charge, and if it's not you, they are required by their very nature to step up to the plate. All dogs need to know their place in the pack, AT THE BOTTOM, so they are not pressured to take control of things and are free to just be a dog. Note also that a pack heirarchy is linear--to prevent dominance problems, ALL family members must be above the dog. Just Dad being in charge isn't enough, because even though the dog reports to Dad, Mom & the kids may report to the dog! This makes a corrective bite to any of them--his subordinates--fully justified, in the dog's eyes. Remember, think like a dog...because he can't think like a human.
That said, here are some suggestions for handling a dominant canine. It's NOT by any means all-inclusive, and is still a work in progress :)  Much of it is geared towards bringing up the unusually dominant or extreme-alpha pup, during the "testing" phases he will put you through as he tries to secure himself the top spot in your family. Keep in mind that this comes naturally to him--he is not "mean" or "vicious", he just feels that he is the most qualified candidate for the alpha position. *Your* job is to teach him that this position has already been filled, and dogs need not apply. Remember, too, that every dog is an individual...and what works on one will not work on them all. The basic issue here is to establish yourself as your problem dog's leader, the one he looks to for guidance--instead of having the dog thinking that the responsibilty of providing leadership of the family falls to ~him~.
First steps when you realize you have a dominance problem:

Be aloof &
withdraw much of your attention and his privileges at first. This gives much more value to your attention when he does receive it. If you have a crate, start using it; if not, buy one. Let him spend a sizeable portion of the day in there--he basically becomes the "Invisible Dog": his basic needs are met, but otherwise he does not exist. Gradually increase affection and privileges as the dog earns them. A fenced yard can be used in place of (or in conjunction with) the crate...if your yard is not fenced, a chain link "dog lot" is relatively inexpensive and will do in a pinch.
Ideally, if his behavior allows for it, you could simply ignore him *in your presence*, a technique known as
social isolation. Read more about this HERE.
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Leadership, dominance, and aggression