It started with a belch and ended with a bite. But it was the kick in between that made UFC 1, celebrating its 25th birthday Monday, truly memorable.

It came out of nowhere, a visceral shock to the system, violence in a moment we'd been trained to expect anything but—when a man was down on his knees. Remember those quaint old days when attacking someone on the ground was as uncouth an act as you could imagine? Few do, but it's part of UFC's lasting legacy, one that began in the first 30 seconds of its first televised fight.

If you've seen it, it's probably seared into your memory. If not, it happened like this. Former sumo wrestler Teila Tuli had lost his balance against Dutch karate star Gerard Gordeau, and they both slammed into the wall of the Octagon. As Tuli attempted to right himself, the kick from Gordeau was already coming, a right roundhouse right to the kisser, launching both Tuli's tooth into the crowd and a martial arts revolution.

Before the bout, no one was really sure what to expect. Many, including participants like future UFC Hall of Famer Ken Shamrock, were waiting for the big reveal, that predictable moment when one of the organizers would finally smarten them up, confessing that this was just another pro wrestling promotion trying to put one over on a gullible public.

No one, Shamrock thought, would be crazy enough to air what was essentially an honest-to-goodness street fight on live television. Scott Bessac, a student of Shamrock's, had brought him an advertisement for the event in Black Belt magazine and had even called matchmaker Art Davie thinking it would be right up Ken's alley.

When he brought it to his mentor, Shamrock just laughed.

"I was like, 'Dude, this is wrestling,'" Shamrock says. "'This is not real. It's fake.' He goes, 'No, no. I talked to them. It's anything. Anything goes.' And I was like, 'Scott, it's wrestling.' Just to prove him wrong, I said I'd check it out. Really, come on? That's not happening. Street fight, you get arrested for it, that ain't happening, so in my mind there's no chance."

Shamrock was a skeptic right up until the moment Tuli's tooth went flying through the air, almost hitting color commentator Kathy Long dead in the face. For a moment there was silence in the bowels of the arena as the next men up processed what had just happened. The energy was electric.

"The locker room went silent," Shamrock remembers. "It was literally something that you only see in movies or you see on the street. It was only quiet for one or two seconds, but it felt longer than that. Then people realized what had just happened and just went nuts. I'm jacked up now, like this is real. I'm smiling. I get to fight one guy, no gun, no knife, no weapons, one person. Like this is a dream. I fight on the street just for my pride, and now I'm gonna get paid to do it."

Sitting cageside, David Isaacs, the first UFC president, recalls taking a deep breath and smiling for a very different reason. There were still six fights to go and plenty of potential problems to come. But his most immediate and pressing concern had vanished like Tuli's teeth.

"Our biggest concern, besides fighter safety, was whether the Octagon would hold up," Isaacs said. "When the big sumo wrestler ran into it, we all held our breath. We believed that it would hold up, but we weren't 100 percent sure. That was the thing we got out of that first fight. 'Oh my God, the Octagon is still standing. We're still doing the show.'"

In the television production truck right outside McNichols Sports Arena in Denver, Semaphore Entertainment Group (SEG) executive Campbell McLaren, now running the burgeoning MMA promotion Combate Americas, was suddenly facing a different concern. Yes, it was a sport-defining visual jolt. And sure, the show would go on with an intact Octagon—but for how long?

"There are 11 cameras and you're watching everything," McLaren said. "However, there was only so much to see when the first fight lasts like 30 seconds or something. I remember thinking, 'We've got a three-hour block to fill, but this might be a four-minute show.'"

McLaren's fears were not entirely unwarranted. When the dust settled, the entire show featured just 13 minutes and 25 seconds of actual cage time. Ultimately, it didn't matter. What they presented was so incredible, no one walked away that night angry that the show ran so short. Instead, the martial arts world was left wanting more. Almost 90,000 people bought the event on pay-per-view, tripling internal expectations. Buys continued to grow steadily as new fans were exposed to the sport at video rental places like Blockbuster, where UFC executives say the no-holds-barred events were a surprise hit.

"We had grabbed the tiger by the tail," Davie told Bleacher Report. "It was like a dream. We knew it would be a big hit."

A few months before the first UFC event, Isaacs found himself at his desk surrounded by a growing crowd. On the television they were all watching two Brazilian men fight it out on the beach in Rio de Janeiro, a buzz in the air. McLaren had intercepted a VHS tape called Gracies in Action on its way to obscurity, and the whole office was quickly obsessed with it.

"Was it really safe? Was it a sport?" Isaacs said. "We're watching this tape with Rorion Gracie narrating, saying things like, 'This man has insulted the Gracie family,' and then some scrawny Gracie brother or one of the uncles beating the crap out of him. It was really compelling, and our gut instinct was: 'Holy crap, this is really interesting stuff. How do we do it?'"

A Harvard-trained lawyer who was in the same class as future President Barack Obama, Isaacs was carving out a profoundly weird niche in an unusual business—pay-per-view entertainment. At the time, he says, the pay-per-view pie chart could be roughly divided into three distinct slices: "movies, porn and Mike Tyson."

A tiny sliver, almost too small to see, was where SEG fit in, running concerts for groups like New Kids on the Block and kids' specials from the people behind Thomas the Tank Engine. But with the success of both boxing and professional wrestling, they knew the future was in fighting, whether real or simulated.

"It wasn't by chance that we got into this particular type of thing," Isaacs said. "AAA wrestling from Mexico, karate tournaments ... we were actively looking to get into some sort of combat sport. We didn't know what that would be, and until we met Art [Davie] and Rorion, we probably wouldn't have done something exactly like UFC. But we would have done something in combat sports. Because that was where all the money was."

SEG was a last-ditch, Hail Mary pass from the team behind the infamous Gracies in Action tapes. Davie, an ad executive, had read about Rorion in a 1989 issue of Playboy magazine and saw potential in the family's struggle over the years to prove their martial superiority.

"I helped Rorion with a direct market campaign for his martial arts school and eventually quit my job at the ad agency and convinced him to open up an LLC in Colorado, one of the states I thought would be most likely to allow what we had in mind," Davie said. "We had been rejected by ESPN, Showtime and HBO when I knocked on Bob Meyrowitz's door at SEG."

At SEG, Davie found a kindred spirit in McLaren, a Meyrowitz employee and creative force who was actively looking at demolition derbies among other potentially violent ideas. He immediately saw the appeal in pursuing a kind of human car wreck instead.

"He called Showtime and they said, 'Get the f--k out of here,'" McLaren said in a 2012 interview. "I was last on his list of calls. But we were doing some pretty out-there programming at the time."

After originally calling it "War of the Worlds" and then "World's Best Fighter," the brain trust settled on "Ultimate Fighting Championship." The name tested well and clearly established a pecking order that placed it above boxing and other forms of combat.

"Nothing beats 'ultimate,'" Davie says simply. "Everything else is south of that."

With a name in place, it was time to start promoting the event in earnest. But, it turned out, explaining the concept to the audience at home wasn't nearly as easy as choosing a name. Even designing a poster was a challenge. Eventually they used a blurry photo of what was vaguely martial arts action, and McLaren's tag line "There Are No Rules" captured the eye.

"The easiest way to explain it would have been, 'It's pro wrestling, but real.' But we compared it to the video game Mortal Kombat instead, because we were distancing ourselves, intentionally, from pro wrestling at that point," Isaacs said. "Consciously, as a business strategy. We were like: 'We cannot be associated with wrestling. That would kill us.' Of course, if I could have gotten Hulk Hogan to do it, we would have all crapped our pants with excitement."

Hogan aside, finding fighters willing to compete was a tough task for matchmaker Davie. The first of eight combatants came easily enough—Davie had Rorion choose a family member to represent the art of Gracie jiu-jitsu, a ground-based spinoff of judo that had been battle-tested by his father, Helio, and other family members in Brazil over the decades.

His choice of his 26-year-old brother, Royce, was surprising to some. Older brother Rickson was the family champion and would eventually become a star fighter in Japan. But merely winning the tournament wasn't Rorion's goal. For him, promoting his family's art wasn't a bonus—it was the entire point.

"My objective was to showcase the effectiveness of jiu-jitsu," he said in a 2013 interview. "Royce was a very sweet guy. He actually came from Brazil to help me take care of my house and help my wife take care of the kids. Half the time babysitter, half the time UFC fighter. Maybe he needed a break from helping me change my kids' diapers. So he goes into the UFC, chokes everybody out and comes back and changes diapers again.

"... By putting someone like Royce in the cage, with a skinny body and totally physically unimpressive, we showed everybody that little guys can be tough too if they know Gracie jiu-jitsu. People say, 'If he can do it, I can do it.' That was the message we wanted to put across, and it worked out great."

Royce, who would go on to win three of the first four UFC tournaments, immediately accepted.

"There was no hesitation," he says. "My brother said: 'I'm setting up this tournament. It will be three fights in one night. Would you like to be a part of it?' Growing up as a Gracie, I was waiting for this kind of opportunity. I'm a product of my father's work and his creation. I did what I learned from him my whole life."

Finding seven other fighters to compete with the Gracie representative was the real trick. Davie searched far and wide for recognizable martial arts superstars like kickboxing champion Ernesto Hoost, only to be turned down over and over again. Fighters were just too used to their own set of rules, more comfortable in the world they knew than the unknown UFC represented at the time.

"We'd show martial artists the Gracies in Action tapes to give them an idea of what it was," Isaacs said. "A lot of the times they'd take one look at it, and they'd be like: 'Oh, no. I'm not doing that.' There was this one guy, Herb Perez, who was an Olympic gold medalist in taekwondo. Nice guy, but took one look at what we were doing and was out the f--king door. He knew that that was not the right thing for him."

Rorion left the matchmaking to Davie, with one exception. Like his father before him, who had famously challenged Joe Louis and other stalwarts of the squared circle, Gracie insisted a pugilist be part of the show. Multiple boxers rejected the pitch before Art Jimmerson was willing to sign on for a $20,000 guarantee.

"I wasn't sure what to expect," Jimmerson recalled in a 2010 interview. "They talked about it being somewhat of a reality Mortal Kombat game. Mortal Kombat and Street Fighter were real popular back then, where they had different martial arts in one game. I thought, 'Wow, a video game come to life.' Man, the boxer in those games always lands his jab. Why not me? I was excited because it would be a challenge."

Backstage before his opening-round match with Royce, Jimmerson was aghast. Gordeau was limping around with a tooth embedded in his foot and his broken hand buried in a bucket of ice. Kevin Rosier, an out-of-shape kickboxer who had just stomped Zane Frazier to a pulp in the second fight, appeared to have a broken jaw. What seemed like a fun adventure and a way to walk out with a big check for a little bit of work suddenly seemed like a terrifying mistake.

"These guys had missing teeth, a busted-up face," Jimmerson says. "It was brutal."

His opponent, Royce Gracie, was in his element, preternaturally calm even though his family's reputation rested on his narrow shoulders. He wasn't fighting for himself. He was there representing a system he believed in, one that had passed from father to son and that the family was now looking to share with the entire world.

"In the beginning when my father and my uncles started this, even before UFC, it wasn't about proving who was toughest," Royce said in a 2015 interview. "It was more of a quest to find out which style of martial arts is the best. Other people say their style is the best; we say ours is the best. There's only one way to find out. No rules, no time limit, no gloves, no weight division. Let's jump in a cage and fight until somebody quits."

After some brief circling, Gracie took Jimmerson to the mat. Jimmerson was already way overmatched, and the single boxing glove on his left hand surely didn't help as Royce slithered into the mount.

Jimmerson tapped out with his unencumbered hand, and his corner threw in the towel for good measure. He didn't end up throwing a single punch, perhaps saving himself for a boxing bout with title implications against Orlin Norris less than two months later.

"If it was a video game, Royce was one of those higher-level characters you're supposed to fight at the end," Jimmerson says. "I fought him first and had no idea what to do. I just knew nothing on the ground. I knew nothing."

Preparing for his first bout in the bowels of the arena, Shamrock was unimpressed with the man who would become his fiercest rival.

"I was like, 'He can't do that to me. There's just no way he can do that to me. I'm too strong,'" Shamrock says. "I wasn't anticipating how effective a gi could be. This was another rookie move on my part. Being young and being successful, I was like: 'It doesn't matter what he does. I'm gonna beat everybody anyways.'"

Before he could fight Gracie, Shamrock had to get past local sensation Pat Smith, billed as a ludicrous 250-0. As the two waited for their cue to walk out on live television, Smith and his entourage were mean-mugging Shamrock and his small group of friends and family.

"There was probably 10 or 12 guys we had to walk past that all had these red shirts on," Shamrock remembers. "He says, 'I'm gonna kill you.' He had all those guys around him, seriously like a gang. There was no security there and they're all in our faces."

At one point Smith and Shamrock's adopted father, Bob, even got into a shouting match as Jimmerson and Gracie carefully made their way past the hubbub. Some men might have been shaken by the experience. For Shamrock, it was motivation.

"He said to me, 'I don't feel pain.' And as I was looking across at him, I just kept building and building and building like I was gonna come out of my skin," Shamrock says. "... I remember putting the heel hook on him, didn't even have it really tight, but I knew I had it enough to hurt him. I heard this 'Ow!' and he screamed. After I jumped off him, I was still really amped up. I still wanted to fight. And I asked him, 'You felt that, didn't you?'"

There was a learning curve for the crowd, which jeered both men, thinking they had been witness to a fixed fight. Unfamiliar with ground work, and unable to see much of the action on the mat because most arenas in that era lacked a big screen to provide the television feed, they didn't understand what had happened.

Despite the grumbling in the audience, the victory set up a semifinal match that would help ignite one of the great feuds in MMA history—Shamrock vs. Gracie. On the surface, it was a mismatch: Shamrock looked like a Greek god sculpted from marble, and Gracie looked like, well, the promoter's goofy little brother fooling around in a bathrobe.

"Of all the fighters, Royce was the least impressive physically," Isaacs says. "He's normal. He's about my size. The chance that I would get in there and fight the guys that he would fight, no way.

"And that was Rorion's point. That a normal man could beat someone like Ken Shamrock if he understood Gracie jiu-jitsu. Weight limits didn't matter because in a real fight, you don't have time to find out the weight class of the guy you're about to fight. In a real fight, it happens, and it's going to go down."

As expected, at least in the Gracie camp, the two men's physical disparity ended up meaning little when Gracie wrapped his gi around Shamrock's neck and squeezed. Less than a minute later, Royce's hand was being raised, albeit not without a bit of controversy.

Shamrock had tapped the mat, and Gracie released the hold—only for both to discover the referee had somehow missed the entire exchange and was looking for the fight to continue.

"He's staring at me and I'm on my knees looking up and the whole time I'm thinking, 'I just got choked,'" Shamrock says. "'I just lost.' And I couldn't understand how that could happen to me. I don't do this, I can't lose.

"Royce said: 'You tapped. You tapped.' And I looked at the referee and nodded, because I did. I mean, I lost. There's no question I lost. I said, 'Yeah, I tapped.' And that just tore me up inside to have to say it. It's his job, not mine, to stop the fight. For me to have to not just lose, but say out loud that I lost—I was just like, 'Argh!'"

Shamrock, in truth, was Gracie's only real competition on the night. Only one other fighter in the tournament (Pat Smith) would finish his career with a winning MMA record, and Gracie's opponent in the finals, Gordeau, limped out on a gimpy foot with two badly damaged hands. He would spend months in and out of the hospital in the Netherlands after his return and offered little resistance.

Gracie eventually secured the rear-naked choke, and Gordeau furiously tapped as Royce refused to break the hold. A small trickle of blood was the only tell revealing what actually happened—Gordeau had taken a nibble on his opponent's ear before giving in.

"I knew UFC was going to be special before it even happened," Royce says. "The world wants to know—who is the best fighter? Everyone wants to know, who would win, Muhammad Ali or Bruce Lee? People have this curiosity, and that was what UFC was."

Before the event was over, Davie and Rorion hugged backstage, a dream realized. Then it was off to a masquerade ball where many of the participants danced the night away in tuxedos and masks, including a spry 80-year-old Helio Gracie.

"I got to see the old man dancing and wearing a tux," Rorion says. "He had a great time. Of course, he was very happy. It was great to experience for the whole family, a historic opportunity for all of us."

The good vibes were fleeting. Soon enough, the UFC would be in a fight for its life. Political pressure began mounting immediately, years before it was kicked off cable systems or banned in state after state. Even UFC II was forced to change to a smaller venue in Denver after the local mayor decided to fight against it.

It was a bout the sport would win in time, altering martial arts permanently and for the better. The seeds of what sport fighting would become are present in that first event, albeit in a much more primitive form. It was no longer enough to claim you were capable of great martial deeds. In a post-UFC world, you had to be able to back it up.

But while the techniques and strategies have changed as the fighters continue to push each other to new heights, one thing was as true in 1993 as it is today—at its best, there's nothing quite like the UFC.

Jonathan Snowden covers combat sports for Bleacher Report. He's the author of three books and is currently working on the biography of UFC 1 star Ken Shamrock.