A peerless Sebastian Vettel leapfrogged Fernando Alonso at the top of the world championship on Sunday as the Red Bull driver led from the first corner to win the Korean Grand Prix.
With four races to go starting in India in two weeks, Vettel, the reigning champion who is chasing a third drivers' title in a row, sits atop the standings with 215 points. Alonso, who finished third, is on 209.
It was the 25-year-old German's third win in three races and he will now be favourite to retain his crown, in what had been a highly unpredictable season until he took the championship by the scruff of the neck.
Second at a cool but sunny Yeongam was Vettel's team-mate Mark Webber, who started on pole. It was the first Red Bull one-two of the season.
Alonso's fellow Ferrari driver Felipe Massa, second at Suzuka seven days ago, continued his resurgence with a fourth-placed finish. Lewis Hamilton, who still had title aspirations going into this grand prix, finished down in 10th.
It now looks increasingly like a two-horse race for the title. Hamilton and his McLaren team-mate Jenson Button, who was shunted out moments after the start of the race, admitted they were out of contention.
Fifth was Kimi Raikkonen of Lotus, followed by Nico Hulkenberg in a Force India. Romain Grosjean (Lotus), Jean-Eric Vergne, Daniel Ricciardo (both Toro Rosso) and Hamilton rounded out the top 10.
"Very pleased. Fantastic, I'm very happy," Vettel told the crowd, having celebrated his 25th career victory by jumping on top of his Red Bull with his arms aloft. "It was a fantastic race.
"Towards the end I felt I had a bit more in the tyres," said Vettel, whose front-right tyre in particular was badly worn by the end. He had been warned repeatedly by his anxious team to "look after" his tyres.
He added: "I think it was a perfect day for me and the team.
"We will have to do our best to remain where we are now. We have to just keep it simple and do our job."
Alonso, also a double world champion, put a brave face on losing his lead in the standings. "I think we have to be happy with the performance today, we finished third and fourth, just behind Red Bull, that at the moment are difficult to beat," he said.
"We just need a little last step to be as competitive as Red Bull and I think it will be a beautiful last four races to the end."
He concluded: "Today was better than expected."
Vettel, who started second on the grid behind Webber, nipped in front of his team-mate at the first corner. Behind them Alonso and Hamilton duelled over third place, with the Spaniard winning through.
Button's bad weekend finished almost as soon as the race began. His fine start from lowly 11th was wrecked when Kamui Kobayashi came flying down the inside, smashing into Button and destroying his suspension.
"I've just been hit by Kobayashi. What an idiot!" the McLaren driver and 2009 world champion exclaimed over the team radio.
Also out, not long afterwards, was Nico Rosberg, who retired his Mercedes because of the same incident. The Sauber driver Kobayashi, third last week in his native Japan, was forced into the pits.
He was then landed with a drive-through penalty for causing the early carnage and bowed out soon afterwards when Sauber decided that the damage to his car was too extensive. Kobayashi later apologised to Button and Rosberg.
Vettel, the man in form after victories at the last two races in Singapore and then Japan last week, was in firm command. Webber -- intentionally or not -- was a buffer between the leader and the chasing pack.
The Red Bull duo were exchanging fastest laps in front of a good crowd -- the last two races at Yeongam have failed to attract spectators -- while an improving Massa shoved a struggling Hamilton further down the field.
Third in the championship is Raikkonen, on 167 points, followed by Hamilton (153), Webber (152) and Button (131).
"I was just told by the team that we had a rear-suspension failure, but it was safe to drive so they kept me going," said former world champion Hamilton, who also had some artificial turf caught under his car for the last portion of the race.
"It was tricky to even keep 10th place," he added, conceding that failure to make the podium in the last three races had cost him a shot at another world title in his final season at McLaren before he moves to Mercedes.