Montgomery won recognition by New York state as Lightweight Champion of the World after beating Beau Jack by a fifteen-round unanimous decision on May 21, 1943. Jack won the first round by a wide margin with a flurry of uppercuts and his signature free-wheeling, constant punching from many angles. But Montgomery quickly settled down and scored frequently with a strong straight right that at times had Jack close to a knockout and against which he could find no adequate defense. Jack's eyes were virtually closed during much of the bout, but Montgomery's injuries were restricted to a cut above one eye. A right to the chin briefly knocked Jack to his knees in the eleventh round and he struggled in the remaining rounds. One ringside reporter gave Montgomery eleven rounds to only four for Jack.