It was Sept. 11, 2017, a beautiful day in the Cleveland suburb of Valley View, and fire chief Ken Papesh was anxiously awaiting a visitor.

UFC light heavyweight champion Daniel Cormier was headed to the firehouse to interview heavyweight champ -- and part-time firefighter/paramedic -- Stipe Miocic for the FS1 show "In the Clinch." It was to preview Miocic's title defense against Francis Ngannou on Jan. 20, 2018.

"I told Stipe, 'I'm totally going to fanboy out on Cormier,'" said Papesh, who considered Cormier his second-favorite fighter behind Miocic.

The shoot could not have gone better. Cormier, an emerging UFC television personality, did interviews at the firehouse and at Miocic's Strong Style MMA gym. Afterward, Cormier, Miocic and the production crew went out for dinner.

Papesh was over the moon after getting to interact with Cormier. He even got a picture with his arm slung over the champ's shoulder in the firehouse kitchen.

"Much to my chagrin, currently," Papesh said recently.

The view of Cormier in the Valley View firehouse has changed since that day almost three years ago as bitterness seeped into the narrative of this relationship and rivalry.

Contempt fueled by competitiveness, accusations of petty gamesmanship and implications of dirty fighting serve as a backdrop for Saturday's main event of UFC 252 in Las Vegas, where Miocic will defend his belt against Cormier to conclude one of the greatest trilogies in all of combat sports.

"He was so nice before, but I think Stipe turned a switch in his head in regards to me," Cormier said recently on ESPN's DC and Helwani Show, "and that's good. I'm happy."

Four months after visiting the Valley View Fire Department, following Miocic's unanimous-decision win over Ngannou, Cormier agreed to a superfight. Cormier, the light heavyweight champion, would move up to heavyweight and challenge Miocic for the title in the main event of UFC 226 on July 7, 2018.

According to Papesh, Cormier said at the firehouse that pursuing that fight was something he would not do. Cormier had maintained he wouldn't move up because of his friendship with American Kickboxing Academy teammate -- and former heavyweight champ -- Cain Velasquez. But with Velasquez sidelined by injuries, he encouraged Cormier to move up for the shot at two titles.

To help promote the fight, Cormier and Miocic were picked in January 2018 to coach opposite one another on "The Ultimate Fighter 27."

Cormier texted Miocic and told him he was looking forward to fighting him, but they both needed to make sure they were adequately compensated for a fight that big. At the time, the two were on good terms.

But things started to change during the taping of the show. There wasn't one major incident, but Cormier told ESPN's Ariel Helwani in August 2019 that he felt his personality rubbed Miocic the wrong way.

"I think he's a respectful guy, so he shakes my hand and he says the right things, but I think at his core he's like, 'I can't stand this dude,'" Cormier said. "We're just too different. I'm loud and I'm boisterous and I mess around all the time and I'm always cracking jokes.

"It's not his style."

Cormier also understands how to promote a fight, which was behind much of what's been said during the rivalry, according to Cormier's team. And while his taunting on the show was playful, it doesn't take much to cross a line with Miocic.

"Unfortunately from the fight promotion side, it's probably kind of one-sided," said Bob Cook, Cormier's coach. "DC has to kind of carry both sides a little bit.

"So far, it doesn't seem that Stipe is too interested in promoting the fight. Good for him. He's just working on training and getting ready. But this is also a business for everybody -- for the UFC, for us, for him. Everybody benefits the more successful it is."

Papesh knows the low threshhold Miocic has with what he perceives as trash talk. And if Miocic is bothered by something said outside the firehouse, his colleagues in Valley View feel likewise.

"We're pretty well tight-knit," Papesh said. "Stipe can walk in here after getting knocked out by DC and get his balls busted by us, but God forbid anyone else tries and does that s---. ... In that way, it's like a brotherhood. Your worst enemy is your brother, until somebody else from the outside tries and goes against him. Then, it's game on."

Miocic chuckled at the firefighters' reaction.

"They got my back," he said. "That's what I love about those guys. That's why I love being a fireman, too. It's like a brotherhood. Just good dudes. I wouldn't change it for the world."

What did change was the dynamic between the fighters.

"I have not had a text message from Stipe Miocic in a really long time," Cormier said. "And I have not texted him, either."

Added Miocic: "It doesn't surprise me. I've said it all before. Being in the fight game, you see a lot of things that people do. Like, 'Wow, really?' You were just nice to me. It's a shame."

Cormier knocked Miocic out in the first round on July 7, 2018. Adding insult to that injury, Cormier then engaged in a pro wrestling-style, post-fight shoving match with former champion Brock Lesnar. The UFC's idea at the time was to have Lesnar, one of the biggest stars in MMA history, fight the Miocic-Cormier winner. Cormier hammed it up for the crowd and cameras with Lesnar in the Octagon, which ticked off Miocic further, according to those close to him.

With Miocic asking for a rematch, Cormier turned around and defended the heavyweight title against Derrick Lewis in the main event of UFC 230 on Nov. 3, 2018, in Madison Square Garden.

Miocic was furious.

Marcus Marinelli, Miocic's head coach, said Miocic was offered Velasquez on that card, but Miocic turned it down. He only wanted Cormier and another crack at the belt he had just lost.

"He felt like [Cormier] was taking the easy way out," Papesh said. "Like he was just going to notch some wins as the heavyweight champion without fighting the person that deserved it."

Cormier was up front about why he wanted Lewis. Cormier needed back surgery, which he didn't think would allow him a proper training camp for Miocic. Cormier vs. Lewis came together in less than a month.

"I also knew Derrick Lewis couldn't wrestle," said Cormier, a former Olympic-level wrestler. "I'm like, I think I can get ready to wrestle in three weeks. Even if I needed to just wrestle for 25 minutes.

"I thought it was more respectful of me to say it to Stipe, open and honest: 'I'm not gonna be ready to fight you in three weeks.' That's my compliment to him, I think. I'm telling him that he's too good to be fighting him on that short notice."

Miocic didn't see it that way, and tensions flared when Cormier said in interviews that Miocic didn't deserve the rematch. Cormier thought Miocic should fight someone else and get a win to earn another chance at the belt.

Cormier had back surgery in December 2018 and said he'd likely fight one more time -- against either Lesnar or long-time rival Jon Jones. If those two fights didn't work out, Cormier said, he'd grant Miocic a rematch.

"I think when I beat him, and he wanted the title fight so bad, the behavior that he showed to me I didn't like," Cormier said. "It changed [how I felt about him]."

Miocic became incensed in early 2019 when Cormier continued to chase a fight with Lesnar. Miocic argued that Lesnar had not fought in three years, had not officially won since 2010 and was coming off a performance-enhancing drug suspension. Cormier said Miocic was being a bit hypocritical and would have taken the big payday against Lesnar if he were in the same position.

"When he didn't beat me the first time, the whole narrative kind of changed," Cormier said. "That was another thing that annoyed me. Of course he would have fought Brock -- who wouldn't have?"

Miocic's side isn't so sure about that.

"Stipe just isn't that guy," Papesh said. "Stipe would rather put $100 in his pocket than $1 million in his pocket if it means he gets to maintain his level of integrity. And not in any way, shape or form is that a downgrade for DC and his integrity. It's just Stipe's beliefs, and that's where he's at and that's what he's gonna do."

The Lesnar and Jones fights fell through for Cormier, and the rematch with Miocic was booked for UFC 241 on August 17, 2019. With Cormier ahead on the judges' scorecards, Miocic made a fourth-round adjustment, landing left hands to Cormier's body. The damage led to a TKO stoppage at 4:09 of the fourth round.

This time it was Miocic's turn to play to the cameras. Miocic celebrated in the Octagon with an Irish jig, which he later said he regretted.

Cormier, who said he was not in adequate shape after back surgery nine months earlier, vowed he would fight one more time, and the only opponent he wanted was Miocic. Now, Cormier was the one asking for a rematch.

But it wasn't about to happen anytime soon, and Cormier wasn't happy about it.

Miocic, 37, said he would agree to a third fight, but there were complications. He suffered a torn retina in the second bout with Cormier due to eye pokes, which Miocic said were also an issue in the first fight. Miocic needed several procedures to correct the injury and now needs to wear glasses.

There was speculation Miocic was just making Cormier wait to get back at him. Miocic even flirted with the idea of fighting heavyweight boxing champ Tyson Fury.

Cormier wasn't happy, but he now views it differently.

"For as much as I was hard on him for his stance in regards to the rematch, I've done the exact same thing," Cormier admitted. "I'm not above saying that.

"Looking back, I probably disliked him for a reason that he probably didn't need to be disliked for."

Actually, it was a scary situation for Miocic and his camp. Cody Stevens, a teammate of Miocic at Strong Style, lost vision in one of his eyes during a 2018 fight, and the team saw how he struggled with multiple surgeries and complications. Marinelli said he told referee Herb Dean to watch out for Cormier's eye pokes prior to UFC 241, but they still occurred.

"Maybe he just fights with his hands open more than he should," Marinelli said. "Maybe he does it on purpose. I don't know. I'm not here to judge the guy. I don't know what his intentions are -- only he knows that. I only know that it is a problem, and it's created problems for us.

"Stipe watched [Stevens] go through it, too. We've watched somebody lose their [sight] in front of us. That's why I'm talking to the ref like, 'I've seen the end result of something that really went bad here. Please listen to us.' We want to win the fight, but more importantly I don't want him losing his eye."

Cormier's persistence in pushing for the rematch grated on Miocic, who started to lightly train with contact in January. And just when Miocic was beginning to ramp things up, the coronavirus pandemic hit in March, and Strong Style was shut down. Meanwhile, Miocic's role as a paramedic increased during the pandemic.

"I don't know how many times I've said it, I [told Cormier] I'll fight you, whatever the UFC wants," Miocic said. "I had a torn retina, dude. Give me a break. Like I planned to have a torn retina and then a pandemic hit? That was all in my plans. Like I planned for all that to happen. C'mon now."

Cormier said on DC & Helwani that he was not poking Miocic in the eye purposely and has been working on correcting the issue.

"It kind of sucks that all of a sudden I'm [considered] this dirty fighter," he said.

Cormier also said he watched a recent interview Miocic did with ESPN's Brett Okamoto, and it seemed Miocic's personality changed.

"When did Stipe become this angry guy?" Cormier said.

Miocic disagreed.

"What is he talking about?" Miocic said. "He says some of the weirdest stuff. I don't know. No, why would I be mad at him? What have I said? Maybe I should give him a call and be like, 'Hey dude, I'm not mad at you,' just to make him feel better. I don't know. I don't want him to think I'm mad at him."

Cormier usually watches his fights not long after they're over. Not this time. He didn't watch his second fight with Miocic until this past May, when he knew the third bout would be booked shortly.

Cormier was frustrated by his health and conditioning going into that bout and did not feel like he fought to his full potential. On top of that, Cormier abandoned the wrestling-heavy game plan after a successful first round and slugged it out with Miocic until ultimately being finished.

"I think I fought the dumbest fight I've ever fought," Cormier said. "My hands were low. There was a lot of comfort in my training camp. And because of that comfort, I wasn't in shape. I had to have some real serious questions about myself recently with Bob Cook."

Cormier said this will definitely be his last fight, with the stakes as high as they can get.

"If Stipe wins, he's the greatest heavyweight fighter of all time," Cormier said. "If I win, I'm the greatest heavyweight fighter of all time."

What will happen in the Octagon after the fight? If it's like most rivalries, bitter feelings will yield to mutual respect.

"Those guys will be like best friends, I bet you," said Javier Mendez, Cormier's coach. "Right now it's like, 'We want to prove ourselves to each other, so we'll try to beat the s--- out of each other.' But at the end of the day, when all is said and done, they'll see each other and ... they'll both be very cordial with each other and actually be good friends more than anything."

Miocic said he's willing to let bygones be bygones, and he said "time heals everything."

"I think he's a respectful guy, so he shakes my hand and he says the right things, but I think at his core he's like, 'I can't stand this dude,' We're just too different."

Daniel Cormier

Cormier agreed.

"When you think about a guy, regardless how nice, how friendly he is, when you spend more than 20 minutes in the Octagon with someone it's hard to maintain that friendship," Cormier said. "I think that's where Stipe and I are today. I still respect Stipe. I do. I respect him as a fighter. I respect him even more as a person."

There's even a chance that at some point, the firefighters at Valley View will thaw their icy feelings for Cormier.

"Everybody knows DC is trying to generate revenue for the fight," Papesh said. "We do not appreciate the way he's going about it. He kind of stepped in it when he came into our house and acted one way and then left and acted another way. We don't appreciate that.

"Other than that, we kind of understand. If you make our boy a little extra money, we're happy with that."