Foaled at King Ranch in Texas, Assault was sired by Bold Venture, who had won the Kentucky Derby and Preakness Stakes in 1936.

[2] Described as being "on the delicate side" by his later jockey, Eddie Arcaro, Assault was plagued with injuries and illnesses from the start.

The hoof was permanently deformed, and the colt developed a limp to accommodate the odd shape of his foot;[3] however, the "Club-footed Comet", as he was later dubbed, showed no signs of abnormality when he was at a full gallop.

Throughout his career, Assault also overcame kidney, splint bone, fetlock, knee and bleeding problems.

Aggravated by traffic early in the race, Mehrtens decided to push Assault earlier than usual.

The handicappers saw this as a stamina issue and made Lord Boswell the favorite in the 1½-mile Belmont Stakes.

Two weeks after his Belmont victory, Assault won the Dwyer Stakes, and the general public opinion finally conceded that he was the best three-year-old in training (but that it was also a poor crop to choose from).

However, in a $100,000 winner-take-all match race at Belmont Park on September 27, 1947, Arcaro and Assault lost by eight lengths to Calumet Farm's Armed, ridden by Douglas Dodson.

Assault returned to the track as a five-, six-, and seven-year-old, although he did not display the same sort of winning form he showed as a three- and four-year-old.

[4] Assault was originally intended to be retired after his four-year-old season and stand stud alongside his sire at 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.

Assault was euthanized after falling and breaking his left front leg at the shoulder, dying on September 1, 1971, at age 28.