Cornered by The Alliance, Shamrock fought Enson Inoue in a bout in Vale Tudo Japan '97 that would determine who would fight Kevin Jackson for the newly created UFC Middleweight Championship. After an exciting back and forth battle, in which Shamrock's training proved instrumental to resist the punishment and the exhaustion, Frank knocked Inoue out with a knee, although the match was officially ruled as a disqualification win due to Enson's brother, Egan, running into the ring after Shamrock had knocked out Inoue. Shamrock later stated that this was the toughest fight in his career.