Conor McGregor’s tweet Wednesday, blaring “THE FIGHT IS ON” in all-caps but showing photos of himself and Floyd Mayweather’s father, could have been construed as just another shot at his nemesis’s age during their long-running back-and-forth. However, after developments earlier in the day indicated that Mayweather was planning a major event at a Las Vegas arena in August, the retired boxer confirmed that the fight is, in fact, officially on.

The announcements culminate weeks of negotiating between the two fighter’s camps, including UFC President Dana White. The fight itself has been a year and a half in the making, at least in terms of when Mayweather and McGregor began trading verbal barbs.

Appearing on ESPN, White confirmed that the fight will take place at T-Mobile Arena. Earlier Wednesday, the Nevada Athletic Commission revealed that Mayweather Promotions has been given the go-ahead to promote a boxing event there on Aug. 26.

The 40-year-old Mayweather will be putting his 49-0 record on the line against the 28-year-old McGregor (21-3 in MMA), but as the fight will be boxing-only, the former has already been installed as a heavy favorite. The UFC lightweight champion has never competed in a sanctioned boxing match, although he has been sharing footage of his efforts to train in that sport.

“The impossible deal is now done,” White said on ESPN. He said that the fight would take place at 154 pounds, with 10-ounce gloves. White said that Mayweather Promotions will “build the undercard,” reflecting the event’s boxing-only nature.

White had long downplayed the possibility of the fight taking place, but as McGregor and Mayweather ramped up their own public pushes for it, the UFC president eventually began to work to make it happen. McGregor “has done a lot of good things for his company, and he wanted this,” White said, adding, “At the end of the day, it’s my job to make fights the fans want to see.”

As for McGregor’s underdog status against an undefeated boxer widely regarded as the best of his time, White cited the Irishman’s unwavering confidence. “He is absolutely, 100 percent positive that he wins this fight, and I stopped doubting Conor McGregor a long time ago,” White said.

The UFC head brought up Mayweather’s age and trouble with opponents capable of fighting left-handed, as McGregor can. He also mentioned his man’s power, saying, that when McGregor hits people, “they go down.”

Last month, McGregor announced that he had signed a “record breaking deal” to box against Mayweather, who has not stepped into the ring since September 2015, when he beat Andre Berto to retain his world welterweight title. The sheer novelty of the proposed bout — with a UFC champion who’s never trained strictly as a boxer going up against an undefeated legend of the ring — could push the prize money into absurd territory, with White speculating that Mayweather could get at least $100 million from the fight and McGregor $75 million.

“It will be the biggest fight ever in the history of two people punching each other,” White claimed Wednesday.

“Everybody’s happy with this deal,” White said, adding that the “negotiations with Floyd were great.” That contrasts with comments last month, when he moaned, “I knew this was going to be a nightmare to get done.”

ESPN’s Dan Rafael reported that Mayweather and McGregor originally wanted the fight to take place Sept. 16 but were beaten to the punch, so to speak, by Golden Boy Promotions and K2 Promotions, who will hold the much-anticipated middleweight title bout between Canelo Alvarez and Gennady Golovkin on that date, also at T-Mobile Arena. As part of that deal with MGM Resorts International — the parent company of T-Mobile Arena — any Mayweather-McGregor fight could not take place within three weeks of Alvarez-Golovkin. Aug. 26 is exactly three weeks before Sept. 16.

Alvarez’s promoter, former boxing champion Oscar De La Hoya, sharply criticized Mayweather-McGregor last month in a Facebook post, calling the much-discussed fight a “circus,” and a “disaster” for boxing. “If you thought Mayweather/Pacquiao was a black eye for our sport — a matchup between two of the best pound-for-pound fighters that simply didn’t deliver — just wait until the best boxer of a generation dismantles someone who has never boxed competitively at any level — amateur or professional,” De La Hoya said.

White had acknowledged last month that McGregor “may never fight again” after making so much money, but when asked Wednesday if we’ll ever see McGregor in MMA again, he said “I think we will.” White said that, after taking on Mayweather, McGregor wants to “turn around” and fight again this year.