Legal opinions please, and if you can cite the specific law, all the better.
A fight begins, in which Person A is being very provoking. His demeanor is intimidating, and his body language clearly expresses a desire to get physical.
Person B stands calmly while being harangued by Person A, and only when Person A steps very close to him does B even put up an arm to create more space.
A few more words are said by A, when suddenly B launches forward with his head and hits A in the chin and a fight erupts. The fight lasts a matter of seconds, and B clearly defeats A.
Now, I understand that in law, provocation is no defence, on which basis, B's headbutt could count as assault. But if B maintained that A's words words were that he was 'going to 'F' you up, right now!', is it equally true that it is with the specific, threatening words that an assault begins?