In one of the biggest upsets in championship boxing, the underdog James J. Braddock defeated Max Baer to become the heavyweight champion of the world.

Boxing is a combat sport and martial art. Taking place in a boxing ring, it involves two people – usually wearing protective equipment, such as protective gloves, hand wraps, and mouthguards – throwing punches at each other for a predetermined amount of time.

James Walter Braddock was an American boxer who was the world heavyweight champion from 1935 to 1937.

Maximilian Adelbert Baer Sr. was an American professional boxer and the world heavyweight champion from June 14, 1934, to June 13, 1935. He was known in his time as the Livermore Larupper and Madcap Maxie. Two of his fights were rated Fight of the Year by The Ring magazine. Baer was also a boxing referee, and had occasional roles in film and television. He was the brother of heavyweight boxing contender Buddy Baer and father of actor Max Baer Jr. Baer is rated #22 on The Ring magazine's list of 100 greatest punchers of all time.

At boxing's beginning, the heavyweight division had no weight limit, and historically the weight class has gone with vague or no definition. During the 19th century many heavyweights were 170 pounds or less, though others weighed considerably more. John L. Sullivan was the first widely recognized champion under Marquess of Queensberry rules. Known as the "Boston Strong Boy", Sullivan weighed around 200 pounds when in shape, and helped transition the sport from its bare-knuckle era. Sullivan would be defeated for the title by "Gentleman" Jim Corbett over 21 rounds on September 7, 1892, the first heavyweight titleholder solely under Queensberry rules.