In round 13 of a boxing match at New York City's Madison Square Garden, Primo Carnera knocks out Ernie Schaaf. Schaaf dies four days later.

Primo Carnera (Italian pronunciation: [primo karnra]; 26 October 1906 29 June 1967), nicknamed the Ambling Alp, was an Italian professional boxer and wrestler who reigned as the boxing World Heavyweight Champion from 29 June 1933 to 14 June 1934. He won more fights by knockout than any other heavyweight champion (IBU, NBA, NYSAC) in boxing history.

Boxing (also known as "western boxing" or "pugilism") is a combat sport in which two people, usually wearing protective gloves and other protective equipment such as hand wraps and mouthguards, throw punches at each other for a predetermined amount of time in a boxing ring. More generally, the term "boxing" can refer to any combat sport in which two opponents face each other in a fight using their fists, covered by gloves in most cases, and differentiated according to their rules, such as western boxing, French boxing, Chinese boxing, Thai boxing, kickboxing, and the ancient pygmachia.While humans have fought in hand-to-hand combat since the dawn of human history, the earliest evidence of a form of boxing can be seen in Sumerian Carvings the 3rd and 2nd millennia BC. The earliest evidence of boxing rules date back to Ancient Greece, where boxing was established as an Olympic game in 688 BC. Boxing evolved from 16th- and 18th-century prizefights, largely in Great Britain, to the forerunner of modern boxing in the mid-19th century with the 1867 introduction of the Marquess of Queensberry Rules.

Amateur boxing is both an Olympic and Commonwealth Games sport and is a standard fixture in most international games—it also has its own World Championships. Boxing is overseen by a referee over a series of one-to-three-minute intervals called rounds.

A winner can be resolved before the completion of the rounds when a referee deems an opponent incapable of continuing, disqualification of an opponent, or resignation of an opponent. When the fight reaches the end of its final round with both opponents still standing, the judges' scorecards determine the victor. In case both fighters gain equal scores from the judges, a professional bout is considered a draw. In Olympic boxing, because a winner must be declared, judges award the contest to one fighter on technical criteria.