Conor McGregor said that he would put Jose Aldo away in the first round, but he actually only needed 13 seconds as he landed a vicious knockout shot in the opening exchange of the fight to become the new undisputed UFC featherweight champion.

For all the bad blood and bad words shared between the two fighters for the past year, McGregor lived up to his promise as he stood and traded with Aldo as soon as referee John McCarthy started the fight.

Aldo threw with power but McGregor countered with a beautifully accurate straight left hand that nailed the Brazilian flush in the chin and sent him careening towards the canvas flat on his back.

More from FoxSports

McGregor followed up with a barrage of strikes, but the fight was already over as the referee rushed over to stop Aldo from enduring any further punishment.

The stoppage came at 13 seconds into the first round.

"No power, just precision," McGregor said about the punch that ended the fight. "No speed, just timing. These are fundamentals. That's all it takes. These are four-ounce gloves, that's all it takes when you take my left hand. Nobody can take that left hand shot."

The crowd at the MGM Grand Garden Arena decorated primarily in Ireland's colors erupted as McGregor climbed to the top of the cage to celebrate his victory as he pointed at his fans and supporters throughout the arena.

McGregor has been predicting a dominant victory over Aldo for more than a year, but it's unlikely even he thought it would only take him less than one minute to put away the pound-for-pound best fighter in mixed martial arts.

"Nobody can take that left hand shot," McGregor said after the win. "He's powerful and he's fast, but precision beats power and timing beats speed.

"That's what I saw out there."

In the hours leading up to the fight, the betting lines in Las Vegas shifted with McGregor actually moving from the favorite to the underdog with a lot of money coming in on Aldo at the last minute.

Obviously, McGregor's confidence never waned as he saw exactly what he wanted to do and it took him only one punch to do what no fighter has done in more than nine years as he puts Aldo away and hands the Brazilian only the second loss of his entire career.

"I feel for Jose, he's a phenomenal champion. He was a phenomenal champion and he deserved to go a little bit longer," McGregor said. "But I still feel at the end of the day, precision beats power and timing beats speed every day of the week."

Over the course of 2015, McGregor has gone a perfect 3-0 with two title fights including a second round TKO over Chad Mendes at UFC 189 and then the finish over Aldo on Saturday night. McGregor has remained calm and composed throughout his UFC career, but it was impossible to ignore the magnitude of the moment at UFC 194.

For his part, McGregor says he actually soaked it all in this week and really enjoyed his time becoming champion.

"Yesterday at the weigh-in I didn't want to give up the stage," McGregor said. "The last time in July when I fought that time, I didn't embrace it all and I wanted to just embrace it more because it's over before you even know it and you're like 'I wish I was in the moment a bit more' so this time I was a hell of a lot more getting into the moment and enjoyed the whole process."

As for Aldo, the now former champion was obviously disappointed by his performance and the result on Saturday night. He immediately asked for a rematch although after a 13-second knockout it's unknown if the UFC will look to book the same fight again or give the shot to Frankie Edgar, who won on Friday night with a first round TKO over Mendes at "The Ultimate Fighter" finale.

"I threw a punch and he came back with another cross and that was that," Aldo said. "I think that we need to rematch, it was really not a fight so we need to get back in here."

McGregor has had plenty to say since arriving in the UFC, but to date he's backed up his ever proclamation both inside and outside the Octagon. Stopping Aldo in just 13 seconds was a result no one likely expected, but McGregor now stands tall as the reigning featherweight champion and the king of the UFC.