The full correct name for your fowl is "Modern Game Bantams" These chickens are direct (sort of) decedents of the pit games once shown at No 10 Downing Street. They are no more aggressive (and maybe less so) than a Rhode Island Red or any other domestic chicken. However game chickens have a "craw full of sand" as my old granny would say which means that they don't know the meaning of the word defeat. This means that a battle may last for days. This trait of never admitting defeat by another hen or rooster is why I advocate the removal of the bird being beat on and keeping its victorious nemesis in the flock. Too often when the aggressor bird is returned to the flock after a time out of a few weeks the fracous just starts again right where it left off.