American boxer who was world heavyweight champion from June 22, 1937, when he knocked out James J. Braddock in eight rounds in Chicago, until March 1, 1949, when he briefly retired. During his reign, the longest in the history of any weight division, he successfully defended his title 25 times, more than any other champion in any division, scoring 21 knockouts (his service in the U.S. Army from 1942 to 1945 no doubt prevented him from defending his title many more times). He was known as an extremely accurate and economical knockout puncher.