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This past Tuesday, Nov. 12, the Ultimate Fighting Championship celebrated the 20th anniversary of their first event. Tomorrow night, they promote UFC 167 in Las Vegas. With the main event being a Georges St-Pierre welterweight title defense, it would be one of the biggest cards of the year on its own.

That it takes place this week adds a whole lot more significance to it as it's been dubbed their 20th anniversary show.

As part of the celebration, UFC produced a documentary, Fighting for a Generation: 20 Years of UFC, which premiered last week. While it's not surprising, more than a few observers notice that they almost went out of their way not to mention something that has been intertwined with the company and the sport of mixed martial arts in general since day one: professional wrestling.

When UFC 1 happened, there was very little publicity around it. The advertising budget was nil, with little more than one 30 second ad that aired on the pay-per-view hype channels at the time. Likely the only publication to write anything of substance about it in advance was Dave Meltzer's Wrestling Observer Newsletter.

Also on 11/12, a PPV show called the 'Ultimate Fighting Challenge' [sic] takes place from Denver which is billed as almost an anything goes fight with champions of several different combat sports (shootwrestling, boxing, sumo, karate, jiu-jitsu, kick boxing, etc.)

Why was Meltzer interested? Two of the competitors in the tournament at UFC 1 had done pro wrestling.

Gerard Gordeau was a kickboxer from Holland who had been brought into the UWF in Japan for a match with top star Akira Maeda. The UWF was unique in that it was promoted with the idea that while other pro wrestling was not on the level, the more realistic looking UWF was a completely legitimate, on the level, competitive sport.

In spite of the presence of legit fighters brought in from all over the world, it was still worked pro wrestling the vast majority of the time.

Gordeau made it to the finals, losing to Royce Gracie. Other than the fight being the first UFC tournament finals, it's notable for Gordeau flagrantly cheating by biting Gracie's ear.

In 1995, Gordeau made another crack at MMA in the Vale Tudo Japan tournament (promoted by pro wrestling's Satoru Sayama, the original Tiger Mask), where he was submitted by Yuki Nakai, but not before gouging him in the eye, permanently blinding him. It was Gordeau's last MMA fight.

Unlike Gordeau, fellow UFC 1 competitor Ken Shamrock was a full-time pro wrestler. He started out in South Atlantic Pro Wrestling in the Carolinas, where he met Dean Malenko. Malenko eventually got him booked in the UWF as a regular, as opposed to an exotic attraction the way Gordeau was used.

In the UWF, everyone on the roster was taught how to fight for real using catch wrestling, a wrestling-based form of submission fighting that's slowly dying as a martial art.

After a host of front office problems, the UWF split into three promotions, all of which had their own slant on the UWF style. Shamrock, following the lead of his peers Masakatsu Funaki and Minoru Suzuki, went to Pro Wresting Fujiwara Gumi.

Eventually, the three young stars decided they wanted to test themselves regularly in real shoots, but promotion head Yoshiaki Fujiwara wasn't a fan of the idea. So, they split and formed their own promotion. Called Pancrase (a play on the ancient Olympic sport of Pankration), they started running real matches with modified pro wrestling rules a few months before UFC 1.

Shamrock didn't win the tournament; he lost in the semifinals to eventual winner and early breakout star Royce Gracie.

Still, he returned for subsequent events, fought Gracie to a draw in a non-tournament rematch in early 1995 (which he would have won if the fight had judges) and became the company's first non-tournament champion by defeating amateur-wrestling-great-turned-UWF-offshoot-star Dan Severn for the UFC Superfight Title (now the UFC Heavyweight Title).

While he lost the title in a rematch to Severn, Shamrock was arguably the biggest star in UFC and MMA in general through the end of 1996. With cable companies dropping UFC from pay-per-view, the money dried up, and he went back to pro wrestling, signing with WWE in early 1997.

He returned to MMA after he left WWE, but due to injuries and his refusal to keep up with advances in the sport, he was never the same.

Not all of the pro wrestlers competing in UFC in the early days had the success of Shamrock or Severn. Midwest independent wrestler Geza Kalman Jr went 1-1 in the UFC before going 4-9 in his MMA career.

His only UFC win was over Dieuseul Berto, who wrestled in the '80s as Haiti Kid Berto for Championship Wrestling from Florida before doing some shots for PWFG in the '90s. His daughter Revelina lost an elimination round fight in the current season of The Ultimate Fighter, never making it into the house.

At UFC 13, Tony Halme entered the heavyweight tournament. A former boxer, he had some fame in pro wrestling for New Japan Pro Wrestling under his real name and for WWE as Ludvig Borga. He lost that night and never competed again. His opponent? An aging Greco-Roman wrestler who was also making his UFC debut—Randy Couture.

You can go on and on, especially in the early years. Ultimate Japan, the company's first event in "The Land of the Rising Sun," was co-promoted by Kingdom, a shoot-style pro wrestling promotion. On that card, journeyman pro wrestler Kazushi Sakuraba began his journey to MMA immortality.

Of the 12 fighters on the card, half have done regular worked pro wrestling matches and a seventh (Couture) did a shoot match in a pro wrestling promotion.

When UFC changed ownership, got sanctioned in Nevada and got back on PPV throughout the United States, they were surprisingly stagnant (cards only available on DirecTV did excellent numbers in proportion to the subscriber base) until Shamrock returned.

Parent company Zuffa kept up hope, but when buys dropped again without him around, they had one last idea to get the company to break through: The Ultimate Fighter.

A reality show about journeyman fighters training and living together as they fought in a tournament for a UFC roster spot; the idea was for it to be a "stealth" way to get fights on TV. Even with the more palatable format, they could only get Spike TV to bite if they offered to both buy the time from Spike and pay all of the production costs themselves.

UFC's best chance for the show to succeed was to get the best time slot for their demographic: Monday nights right after WWE Monday Night Raw. Vince McMahon was given the option of vetoing the deal, but he elected not to.

The Ultimate Fighter was a hit, and the finale, headlined by a war of a final and Rich Franklin easily handling Shamrock, cemented UFC as being on the rise. PPV numbers immediately started to go up. While the show was hurt by WWE leaving Spike, it was a blessing in disguise because Spike proceeded to build around UFC, with old fights being used as filler programming.

And then there was Brock Lesnar.

You all know the basics of his story: NCAA national champion wrestler turned WWE prospect who quickly became the WWE Champion but quit after two years on a main roster when he burnt out on the road schedule. After a misguided attempt at making an NFL team and a legal battle with WWE over the terms of his release, he ended up training for MMA.

UFC signed him after his first fight, a one-sided mauling of Korean judoka Min-Soo Kim (who had a 2-5 record before the fight and finished his career at 3-7). Lesnar was fast-tracked instead of being built against journeymen, but UFC was sly about how they did it.

Lesnar's debut in the company was at UFC 81 against former UFC Heavyweight Champion Frank Mir. Mir vacated the title after a motorcycle accident that left him badly hurt, and he wasn't the same. His record was 8-1 before the accident, but in the four fights between the accident and the Lesnar fight, he was batting .500 at 2-2.

It made sense as a fight to present to the casual fans who the show was targeted toward and didn't know about Mir's accident and decline:

If Lesnar won, he beat a former champion and could be elevated quickly.

won, he beat a former champion and could be elevated quickly. If Lesnar lost, he lost to a former champion and could rebound since he was a rookie.

UFC did everything they possible could to get casual fans to buy the show while also trying to appease the hardcores who stuck with them through the bad times. Besides Lesnar "not really" being fast tracked, the card was officially headlined by Tim Sylvia vs Antonio Rodrigo "Minotauro" Nogueira for the UFC Interim Heavyweight Championship (more on that later) with Lesnar vs Mir as the co-main event.

Ads for the show were purchased on WWE programming. Not only that, but UFC licensed Lesnar clips from WWE. The message was clear: NCAA Champion Brock Lesnar wasn't making his UFC debut as much as former WWE Undisputed Champion Brock Lesnar was.

Lesnar lost, but he made a rookie mistake and got caught in a submission after a bad referee call paused the fight when he was pounding Mir out. If he was going to lose, that was the way to do it.

As for business? UFC 81 did 600,000 buys, the sixth biggest show in history up to that point. Perhaps more tellingly, 250,000 of the 600,000 homes that bought it had never purchased a UFC event before (link goes to F4WOnline's subscriber-only forum). The most obvious conclusion was that Lesnar had just brought a ton of wrestling fans over to UFC.

In his next fight, Lesnar scored an incredibly dominant decision win over Heath Herring, who had done pro wrestling in Japan and got his start in an Amarillo, Texas, based MMA promotion that used modified pro wrestling rules. This fight not only established Lesnar as a legitimate threat, as Herring was a top tier heavyweight, but sent Herring packing into retirement.

Three months later, Lesnar was challenging for the UFC Heavyweight Championship. To make a long story short, Randy Couture sued to get out of his contract when UFC couldn't get Fedor Emelianenko, the best heavyweight outside of the promotion. UFC refused to vacate the title as part of their legal strategy, so they set up the aforementioned Nogueira vs. Sylvia fight to determine an interim champion.

When Couture's prospects looked grim, he asked to return to UFC to defend the title against Lesnar, as it was the most lucrative fight he could have. While a Nogueira interim title defense vs. Mir was scheduled for UFC 92 in December 2008, UFC ended up with a hole in their schedule, and Couture vs. Lesnar for the lineal title was made for a month earlier.

With Couture being a small heavyweight and Lesnar cutting weight to make the 265-pound limit, the size difference just looked wrong, especially when they clinched.

Couture's wrestling was sharp enough that he was able to defend Lesnar's takedowns, but he couldn't train for Lesnar's size. So, he was stopped by a TKO in the second round by a punch that he would have successfully slipped if fighting someone that didn't need custom-made size-4XL gloves.

A month later, with Nogueira ill and not himself, Mir became the first person to knock him out. Lesnar, at ringside, looked about the happiest I can possibly imagine that man looking. After delays due to injuries, the match was made as the main event for UFC 100. Lesnar stopped Mir in the second round with punches on the ground and looked unstoppable.

Stacked with main event level matchups three fights deep (Georges St. Pierre vs. Thiago Alves and Dan Henderson vs. Michael Bisping supported Lesnar-Mir) and boosted by the UFC 100 name, expectations were high. UFC President Dana White even promised to jump off the roof of the Mandalay Bay Resort and Casino if the show hit 1.5 million buys.

He had to learn how to base jump as the show did 1.6 million PPV buys, a non-boxing record. The pro wrestling record is a little under 1.22 million buys for WWE WrestleMania XXVIII (John Cena vs. The Rock I), and that number includes overseas buys while the UFC number only includes the United States and Canada.

Unfortunately for Lesnar, through dietary habits lacking in vegetables, he developed diverticulitis. The chronic intestinal issues kept him out of action for long periods of time, and he was never the same as a fighter.

After an incredible come from behind victory over Shane Carwin, the only fighter close to being another Brock Lesnar in terms of on-paper size and skills, he came back three months later to lose the title to current champion Cain Velasquez.

Over a year later, he returned to face debuting Dutch kickboxer Alistair Overeem in a title eliminator fight. Overeem picked him apart, stopping him with hard kicks and knees to the body a little less than halfway into the first round.

Lesnar announced his retirement after the fight, something he planned on doing regardless of the outcome after the title shot if he got that opportunity. As you all know, he returned to WWE as a part-time attraction a few months later.

UFC Heavyweight Champions Who Have Done Pro Wrestling Fighter Pro Wrestling Involvement Ken Shamrock Independent promotions '89-'90, traditional & shootstyle Japanese pro wrestling '89-93, WWE '97-'99, TNA '02. Dan Severn Shoot-style in Japan's UWFI, traditional pro wrestling in the U.S. & Japan as NWA World Heavyweight Champion. Mark Coleman Traditonal pro wrestling in Japan late in his MMA career. Maurice Smith Shoot-style pro wrestling in Japan's UWF. Randy Couture* A shoot fight in RINGS, a shoot-style promotion that had started promoting legitimate shoots most of the time. Bas Rutten Did traditional Japanese pro wrestling for about a year after retiring from MMA. Was an incredibly gifted in-ring performer. Kevin Randleman Traditonal pro wrestling in Japan as Mark Coleman's partner. Josh Barnett Traditional and shoot-style wrestling in various Japanese promotions when he was suspended by American athletic commissions. Ricco Rodriguez A tag team match on a Japanese card promoted by Antonio Inoki featuring major stars from MMA and pro wrestling doing traditional pro wrestling. Brock Lesnar Former WWE champion who returned to WWE as an attraction after retiring from MMA competition. Wrestling Observer Newsletter

If you include the lineage of the UFC Superfight Title, 17 men have been UFC Heavweight Champion. No matter how you calculate it, more than half have done pro wrestling. The two industries have a long history of cross-pollination, and there's so much more ground that can be covered that I don't have space for, like how UFC matchmaker Joe Silva tried to model the lightweight division after WCW's cruiserweights.

I'll end on this note: I got into UFC when my dad came home from work one night in 1994 with a press kit for UFC 2 that included a screener copy of the home video release.

Without the coverage of UFC in the wrestling newsletters at the time, I would have been completely lost, especially with my local cable company being the first to drop UFC and other MMA events and the home video versions of UFC events taking a year to come out.

If not for the connections between pro wrestling and MMA, I wouldn't have been able to give any context to what was happening (the announcers couldn't back then, either) or stuck with it in any form.

David Bixenspan has been Bleacher Report's WWE Team Leader and a contracted columnist since 2011. You can follow him on Twitter @davidbix and check out his wrestling podcasts at LLTPod.com.