After failing to become a professional baseball player, Marciano took up boxing and became one of the greatest boxers of all time. Hard-punching and durable, he was the heavyweight champion from 1952 to 1956—and the only one to have retired without a defeat or draw in his professional career. He died in a plane crash in 1969, on the eve of his 46th birthday, while en route to Des Moines, Iowa, where a surprise birthday party awaited him. Of his 49 professional wins, how many were by knockout? Discuss