For the first few minutes of Daniel Cormier’s heavyweight superfight with Stipe Miocic, size appeared to matter as the two locked up against the fence.

But when Cormier (21-1 MMA, 10-1 UFC) got free, his power evened the score with a short right hook that knocked out Miocic (18-3 MMA, 12-3 UFC) and made him the second simultaneous two-division champion in UFC history.

The heavyweight title bout was the main event of today’s UFC 226 show at T-Mobile Arena in Las Vegas. It aired on pay-per-view following prelims on FS1 and UFC Fight Pass.

Cormier’s trip to the history books was made official at the 4:33 mark of the opening frame. After dropping Miocic, he stood overhead and landed a burst of punches that left no doubt he was the winner.

“I uh, I was a heavyweight for a long time, and I left the division,” he said. “I never knew what I could become, but tonight I got the answer: I’m a two-division champion, baby!”

Cormier, who joins Conor McGregor in the rarified air of fighters to hold belts simultaneously in two divisions, called out a cageside Brock Lesnar, whose presence was picked up by cameras just moments before Saturday’s headliner. The WWE heavyweight champ then entered the octagon and immediately shoved the new UFC champ. The two then engaged in a shoving and shouting match that more closely resembled a pre-fabricated pro-wrestling angle than a legitimate faceoff between combatants.

“Push me now, you go to sleep later,” Cormier said after Lesnar got physical.

Lesnar returned to the heel role he enjoyed in the octagon during his UFC championship fight against rival Frank Mir, berating Miocic and Cormier.

“Miocic is a piece of (expletive) … ” he shouted. “D.C, I’m coming for you, motherf(expletive).”

After months of flirtation, Lesnar is once again a UFC fighter. Two years ago at UFC 200, he returned to the octagon after a five-year layoff to smother Mark Hunt. But the glow from his win was short lived when pre- and post-fight drug tests by the U.S. Anti-Doping Agency turned up positive for the estrogen blocker clomiphene. The result ultimately was overturned, and he was given a one-year suspension.

USADA, which approved a UFC-requested exemption to waive a four-month waiting period for drug testing, was forced to answer why the positive result came after the fight. Hunt later sued the UFC, alleging the promotion conspired to put him in the octagon against a doped fighter.

It remains to be seen how the UFC handles a six-month waiting period required of un-retiring fighters – a rule modified by USADA in the wake of the Lesnar scandal – for the fight with Cormier. But with the skirmish inside the octagon at UFC 226, the promotion has its first piece of footage to use to promote the upcoming fight.

Cormier, the No. 3 fighter in the USA TODAY Sports/MMAjunkie MMA pound-for-pound rankings and the No. 2-ranked light heavyweight, came into the UFC 226 headliner sporting a bulk he hadn’t felt since 2013, when he battered heavyweight Roy Nelson for his third UFC win in the big-man division. Miocic immediately put his size to work, putting Cormier on the mat. When Cormier got back to his feet, the heavyweight champ held him there.

At distance, Miocic popped Cormier with a knee and went to work with combinations. Cormier replied with an uppercut up the middle and attacked the legs.

Following one exchange, Miocic complained of an eyepoke, and replays showed an egregious rake from Cormier. Referee Marc Goddard warned him for the infraction.

After the restart, Cormier began finding success on the inside. Then, he caught Miocic with his hands down after a clinch, and quickly pounced to seal the deal.

Cormier, nearly in tears, initially was speechless as he held two UFC belts. But that didn’t last long.

“I am 39 years old, and I’ve been second a lot of times,” said Cormier, who also became the fifth fighter to hold belts in multiple divisions alongside McGregor, Randy Couture, B.J. Penn, and Georges St-Pierre. “But today, I finally accomplished everything.”

Well, there’s one last thing: To take down the biggest physical opponent of his career, and likely the biggest payday to boot.

Up-to-the-minute UFC 226 results include:

Daniel Cormier def. Stipe Miocic via knockout (punches) – Round 1, 4:33 – to win heavyweight title Derrick Lewis def. Francis Ngannou via split decision (29-28, 29-28, 30-27) Mike Perry def. Paul Felder via split decision (29-28, 28-29, 29-28) Anthony Pettis def. Michael Chiesa via submission (triangle armbar) – Round 2, 0:52 Khalil Rountree def. Gokhan Saki via knockout (punches) – Round 1, 1:36 Paulo Costa def. Uriah Hall via TKO (punches) – Round 2, 2:38 Raphael Assuncao def. Rob Font via unanimous decision (30-27, 30-27, 30-27) Drakkar Klose def. Lando Vannata via unanimous decison (30-27, 30-27, 30-27) Curtis Millender def. Max Griffin via unanimous decision (29-28, 29-28, 29-28) Dan Hooker def. Gilbert Burns via knockout (punches) – Round 1, 2:28 Emily Whitmire def. Jamie Moyle via unanimous decison (29-28, 29-28, 29-28)

For complete coverage of UFC 226, check out the UFC Events section of the site.

(MMAjunkie’s Mike Bohn, John Morgan and Ken Hathaway contributed to this report on site in Las Vegas.)