Terriers are fearless. Some times too brave for their own good. We had a Cairn who mixed it up with a trespassing German Shepherd and he was lucky to survive. He had to wear one of those plastic (`Elizabethan’) collars and bumped into things for weeks.
Keep in mind, “pit bills” (sui generis) are terriers bred with old English bulldogs.
When bull baiting was banned, English `sports’ started ratting contests, legal, and even dog fights, illegal, which could be done in-doors. Believe they ban pit bulls now.
The two Jack Russell’s I had before the pups I have now were also fearless. They are a big dog in a little dog’s body. One of them got out of the fence once and ran across the road after a groundhog. My daughter caught up with him just in time to pull him tail first out of the groundhog den. That same groundhog killed my neighbor’s Beagle just a couple of days before that. We finally did away with that groundhog but you are right, they are fearless! Both JRT’s lived to the ripe old age of 14+ before passing but I don’t know how. LOL