On March 26, 1943, a chestnut colt was born on King Ranch, a large Texan ranch owned by Robert Kleberg Jr. He sire, Bold Venture, had won the 1936 Kentucky Derby and Preakness Stakes, while his dam, Igual, was an unraced mare. However, her sire is two-time Horse of the Year Equipoise. Her dam's dam is Masda, Man o' War's full sister.
As a young horse, the chestnut colt, named Assault, stepped on a stake, permanently crippling himself. When Assault first trotted before trainer Max Hirsch, the man doubted whether he would ever be able to race. He raced four times before winning a race.
Because of the war, travel was highly restricted, so the Flash Stakes was held on at Belmont on August 5 instead of at Saratoga. he ended up finishing in a four-way photo finish.
Next he finished third in the Babylon Stakes, with Southern Pride and Tidy Bid in front of him. In the Cowdin Stakes, he finished fourth behind Knockdown, revoked, and Southern Pride. After winning only two out of nine races that season, he was sent to South Carolina.