LAS VEGAS -- With the location intact, Khabib Nurmagomedov attempted to settle his grudge war with Conor McGregor at UFC 229 on Saturday and did everything he said he would in the lead-up. Nurmagomedov (27-0) relied on his superior grappling skills to maul the former champion on the ground and defend his UFC lightweight title via fourth-round submission at T-Mobile Arena in the biggest fight in UFC history.

That's when all hell broke loose.

Chaos ensued inside the Octagon immediately after McGregor tapped out via rear-naked choke in Round 4 as members of both teams began to fight with Khabib's team appearing to start the insanity. The melee quickly spilled out into the ringside area as police restrained a number of fans who jumped the barricade. Nurmagomedov got into a shouting match with UFC president Dana White during the altercation inside the cage. After order was relatively restored and McGregor was escorted to the locker room, UFC chose to skip Nurmagomedov's traditional post-fight interview in order to play it safe.

"If I put this belt on you, everybody's going to start throwing shit into the Octagon," White told Nurmagomedov.

The post-fight scene was one of the ugliest in UFC's history. After emerging victorious, Nurmagomedov was in no rush to simply leave the beef in the cage. He stood over the fallen McGregor, shouted some words in his direction and appeared to even spit on him as he was recovering. The champion then turned his attention to the cage-side area, specifically McGregor friend and Bellator MMA fighter, Dillon Danis. Nurmagomedov scaled the Octagon cage and leaped in the direction of Danis and numerous others. 

What's more, as the melee was taking place on the outside, matters were made worse back inside the cage. Three members of Nurmagomedov's team attacked McGregor, sending the entire T-Mobile Arena into a frenzy the likes of which mixed martial arts has never seen before. Arrests were made, spectators were escorted from the building and one of the biggest nights in combat sports history was left with quite possibly the biggest black eye it's ever been dealt. 

The dislike between the two camps escalated on April 5, just two days after Nurmagomedov slapped McGregor teammate Artem Lobov for comments he made about the Russian fighter on social media. McGregor, who ended a nearly two-year layoff on Saturday, showed up unannounced at UFC 223 in Brooklyn, New York, and attacked a bus filled with UFC fighters including Nurmagomedov.

McGregor, who tossed a hand truck through the window and injured three people, avoided jail time by pleading guilty to felony assault charges and accepted a plea deal. The hostility between the fighter's camps and the respective fans of their home countries helped build their title bout into an event that White expects to possibly double UFC's pay-per-view record of 1.65 million buys from McGregor's rematch with Nate Diaz in 2016.

It remains unknown whether the post-fight attack on McGregor and his team was a calculated and direct response to the bus attack at the Barclays Center. Either way, it marred what had been an intense and dramatic title bout featuring current and former champions, and two fighters with contrasting styles.

After McGregor (21-4) stuffed an early takedown attempt in Round 1, Nurmagomedov was successful on a follow-up attempt and spent the majority of the opening round grappling for position as McGregor was seated. Eventually, Nurmagomedov worked him to the ground and landed a huge right hand at the horn to end the round.

The second round was Nurmagomedov's most dominant. He dropped McGregor briefly with a violent counter right hand that turned his chin in the early going. McGregor rose to land a knee to the face, but shortly after, Nurmagomedov secured another takedown and mauled McGregor for the remainder of the round with elbows and punches.

McGregor, who was lucky to survive, worked to his feet to close the one-sided round and talked trash to Nurmagomedov, which forced Dean to restrain the Russian champion. The crowd roared in approval of McGregor's toughness and the momentum carried with him into Round 3 as he largely outboxed Nurmagomedov on his feet and stuffed two of three takedown attempts.

But with his gas tank depleted after spending the majority of the fight on his back, McGregor gave up an early takedown in Round 4 and eventually gave up his back to avoid dealing with Nurmagomedov in full mount. "The Eagle" quickly applied a rear-naked choke from behind and forced the tap at 3:03 of Round 4 to make the first defense of the vacant title he won by defeating late replacement Al Iaquinta in April.

All three judges had Nurmagomedov leading 29-27 at the time of the stoppage.

The loss was the first for McGregor since he faded against Nate Diaz at UFC 196 in their first meeting and tapped out via similar choke. During the two years since McGregor moved up in weight to capture the lightweight title from Eddie Alvarez at UFC 205, he also suffered a loss in his pro boxing debut against Floyd Mayweather in August 2017.

Nurmagomedov took home a disclosed purse of $2 million, according to the Nevada State Athletic Commission. McGregor, meanwhile, earned $3 million and claimed at Thursday's final press conference he could earn as much as $50 million should the fight exceed two million PPV buys.

UFC 229 results

Khabib Nurmagomedov (c) def. Conor McGregor via third-round submission to retain the lightweight title
Tony Ferguson def. Anthony Pettis via second-round TKO (stoppage, broken hand)
Dominick Reyes def. Ovince Saint Preux via unanimous decision (30-27, x 3)  
Derrick Lewis def. Alexander Volkov via third-round TKO
Michelle Waterson def. Felice Herrig via unanimous decision (30-26, 29-28, 30-27)  
Jussier Formiga def. Sergio Pettis via unanimous decision (30-26, 29-28, 29-28)  
Vincente Luque def. Jalin Turner via first-round TKO (punches)
Aspen Ladd def. Tonya Evinger via first-round TKO (punches)
Scott Holtzman def. Alan Patrick via third-round TKO (elbows) 

UFC 229 highlights

CBS Sports was be with you for every punch, kick and submission attempt on Saturday night with analysis, updates and highlights below. If you are having trouble viewing the application, please click here.  

Thanks for stopping by.