The English bull terrier was originally bred to herd bulls, in an effort to find a dog that was faster and more agile than the bulldog. Its ancestry includes the British bulldog, the fox terrier and the Dalmatian.
Because of its tenacity, fearlessness and powerful jaws, the bull terrier was later used as a fighting dog. Like any dog that was bred to fight other dogs, the bull terrier is very determined and tenacious. It had to be strong and able to grab the other dog and hang on with its powerful jaws, regardless of any injury to itself or the size and strength of its opponent. This tenacity was also one of the reasons it was so successful at herding bulls. Bulls are extremely stubborn creatures, unpredictable and easy to anger. They would have had no hesitation retaliating and attacking with their horns, goring the dog or sending it flying through the air.
Bull terriers were not bred to attack people, and in fact they make loyal and lovable family pets. They are trusted and cherished by many dog owners, including myself. They do have a tendency to be aggressive towards other dogs, however, but if they are well trained and closely controlled, this does not usually present a problem.