The American boxer who was world heavyweight champion from June 22, 1937 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. Who is he?