In 1939, Riddle turned down an offer of a then unheard of $1 million for Man o' War.

Seabiscuit beat his uncle, 1937 Triple-Crown winner War Admiral, by 4 lengths in a 2-horse special at Pimlico and was voted American Horse of the Year for 1938.

Some modern breeders design matings to concentrate the influence of Man o' War through deep inbreeding. For example, he appears at least 22 times in the bloodline of American Pharoah.

Man o' War made a stunning debut in his maiden race at Belmont Park on June 6, 1919. Despite having jockey Johnny Loftus restraining him throughout the race, Man o' War won by an easy six lengths and made quite an impression in the papers. "He made half-a-dozen high-class youngsters look like $200 horses," wrote the turf editor of the New York Morning Telegraph.

Man o' War won the Stuyvesant Handicap easily against only one rival, the gelding Yellow Hand. His odds of 1 to 100 are believed to be the shortest ever offered in an American horserace.

Had he raced at age four, the handicappers would have started him at 140 pounds, increasing the weight each time he won until Man o' War either lost or was injured. For this reason, Riddle decided to retire him at the end of his three-year-old campaign. He retired as the then-leading money-earner in American history.

Man o' War was retired from stud in 1943 after suffering a heart attack. He died on November 1, 1947 at age 30 of another apparent heart attack.

Kummer rode the Man o' War to nine wins in nine starts.

His sire was Fair Play and his dam was Mahubah, the daughter of Rock Sand, the 1903 winner of Britain's version of the Triple Crown.

The original owners intended to race Man o' War themselves, but in the summer of 1918 they decided to liquidate their racing stable due to the ongoing war effort. Riddle purchased the rangy colt, who seemed too large for a yearling, for just $5,000.