Another popular spectator sport is professional wrestling, locally known as "puroresu" (プロレス). While the sport was known in Japan before World War II, it did not become widely popular until the rise of Rikidōzan, considered the "father" of puroresu, in the 1950s. While similar to professional wrestling in the rest of the world in that winners are decided before the match, puroresu has become a unique style. Most match storylines play up the wrestlers' "fighting spirit". Also, because many Japanese wrestlers have martial arts backgrounds, most strikes during matches make full contact. Puroresu also enjoys close ties to mixed martial arts, with some companies often holding wrestling matches and MMA fights in the same event; because of this, both wrestlers and fans treat puroresu as a combat sport.