In an aggressive behavior resulting from the interaction of two exemplars, the dominance is the most common cause of its origin.
As for the why of these behaviors, we can think of several circumstances or unchaining conducts from theor the owners. One of them is the intrinsically dominant character of determine breeds (Rottweiler, bull terrier, etc.), between which, by means of a rigorous selection, the breeders look to strengthen to all levels, including the dominant character which is inherent to this breeds.
Logically, the problem gets serious if to this we add not only the tolerant attitude and even pleasing from some of the owners, but also if he comes out as victor of the incident, which will make him repeat it frequently, as a way to accentuate his dominance. In any circumstance, the repetition reinforces the pattern.
Besides the already quoted, there also exists other circumstances that can motivate a dog to attack another as a consequence of an excessive dominance.
A lack of authority inside the family group can end in an aggressive manifestation from the dog towards one or more members of the same. This lack of authority is determinant at the time of locating the dog inside the hierarchic structure, in which all the family members are positioned by him.
As a consequence of the exposed, if the dog thinks that not only can he challenge a human, but even win over him (on normal circumstances, humans are toas semi-gods), you will understand then, that with more reason, the same will happen with another dog. Another usual cause is the aggression to another exemplary as consequence of the sentiment of possession to another exemplary or dominance over a third exemplary in dispute, generally of the opposite sex. This can happen when the rival tries to have the exclusive attention from the third exemplary or if she is a female, to initiate the coupling rites.
All the circumstances can be strengthen if the event takes place inside the territorial environment of the exemplary that suffers this problem, although who really suffers its effects is the owner.
However, the tendency of the rules to mitigate or eradicate this behavior, can be put into action in several ways, depending on the origin of the same.
Besides the age of the dog and the time that it has past from the beginning of the problem, for the cases in which the point to start is a dominant character (usual to his breed), with reinforced repetition or without it, you must never run from the possible contact with other.
It will even be convenient to strengthen these encounters in a controlled way, looking so, for the negative answer of our dog to, in this way, express our rejection to this posture the cases of aggressions by a third exemplary can be understandable, if there is the attention of a female to capture. But we shouldn't tolerate it, not only to avoid injuries between them, but also to stop the annoying consequences of the differences of opinion from the other owners.
Finally, if this behavior would be motivated or aggravated by a lack of authority in a family level, not only you will have to act as mentioned above, but you also must adopt the necessary measures, with a tendency to increase this level.