On March 1, 1949, Joe Louis, who had held the world heavyweight title for almost 12 years, longer than anyone else in history, announced his retirement at age 34. Having defeated Jersey Joe Walcott in his last fight the previous year, he finished with a record of 63-3, which included 25 successful title defenses and 49 knockouts.

However, during his fabled career, Joe had earned about $5 million, most of which he either gave away or spent. In the late 1940s, the IRS assessed Louis more than $1,000,000 in back taxes and penalties. This arose as a result of a divorce settlement in which Louis agreed to pay his ex-wife a portion of the purse from his biggest fight, $650,000. It was based on a percentage of his winnings, as a manager's fee would be computed, but the IRS considered it to be alimony, ruling that Louis owed taxes and considerable penalties on money. Louis knew only one way to earn that kind of money, so he returned to the ring.

Coming out of retirement on September 27, 1950, he challenged the new champion, Ezzard Charles, but was beaten decisively in 15 rounds. He attempted another major bout on October 26, 1951, against future champion Rocky Marciano; this time he was knocked out in the eighth round. Louis never fought again, ending his extraordinary 17-year career with a record of 68 wins and three losses, winning 54 of his fights by knockouts.

Watch some of Joe Louis' greatest knockouts below: