John L. Sullivan was the last Bare-Knuckle Boxing Heavyweight Champion of the World and the first Gloved Heavyweight Champion of the World. Of course, back when the “world” mostly meant the US and the UK to citizens of these countries.
But these fighters were tough, with fights sometimes lasting as many as 45 rounds (3 hours) and often with no legitimate end other than knockout allowed.
Interestingly, some think bare knuckle is safer than using gloves. There is evidence to show that its the jarring of the brain, not the damage caused to the outside of the head, that causes long-term issues like CTE. Bare-knuckle boxers, it seems, were more strategic in their shots, since any strike might end up breaking your hand (and losing you the fight).
“A man fights with his head almost as much as he does with his fists. He must know where to send his blows so they may do the most good. He must economize his strength and not score a hit just for the sake of scoring it. Learn to strike straight and clean. Swinging blows nearly always leave an opening for your opponent. … Always watch your opponent. As soon as you see him about to lead, shoot your left into his face. The force of his coming towards you will increase your blows considerably….I endeavor to hit my man above the heart or under the chin or behind the ear…A man wears out pretty soon if one can keep hammering away in the region around the heart. A blow under the chin or behind the ear will knock a man out quicker than a hundred blows on the cheek or any other portion of the face. I have always considered it necessary that a young man, in order to become an accomplished boxer, should have brains as well as muscle. I never knew a thick-headed fellow yet to become skillful in the manly art….What I know about boxing, I picked up from hard experience and intelligent observation. I belong to no school of boxers and have copied no special master’s style. I always fight according to my own judgment. If a man can’t train himself, no one in the world can do it for him.”
John L. Sullivan
Note the Man Sau / Wu Sau like positioning of the arms and the Sunfist (thumb up) position of the hands.