Assault was originally intended to be retired after his four-year-old season and stand stud alongside his sire at King Ranch. However, none of the mares he was mated with became pregnant; it was apparent that he was sterile . He was returned to racing until the age of seven, where he won a few more races, including one more running of the Brooklyn Handicap . He was then permanently retired to King Ranch. There were some rumors that he was allowed to pasture breed with some of King Ranch's Quarter Horse mares, but there are no records that any of those foals made it to the track. He did sire two Quarter Horse foals, and they were registered with American Quarter Horse Association [ citation needed ] . Assault died on September 1, 1971, at age 28, at King Ranch. The gravesite is on the King Ranch (in Kingsville, Texas ).