Lee Sedol started with a bow, a traditional Korean gesture of respect for an opponent who could neither see him nor sense his presence.

The world champion at Go – an ancient Chinese board game – looked nervous. His eyes darted from side to side. He took a sip of water, and made his first move.

Lee could be forgiven some nerves: his opponent was AlphaGo, an artificial-intelligence program designed by Google DeepMind, their five-game series billed as a landmark face-off between human and computer. “History is really being made here,” said commentator Chris Garlock, as the first game in the series started.

Three and a half hours later, history had indeed been made: AlphaGo won, shocking many observers of the game and marking a major breakthrough for AI.

Go isn’t played much in the west, but it is widely enjoyed throughout east Asia. Two players take turns to place tiles on a board, trying to gain territory by arranging their tiles in strategic shapes or patterns. The surface level simplicity is deceptive: there are trillions of possible moves. The almost endless possibilities make it difficult to follow a particular strategy, and mastering the game means using intuition to react to any number of possible twists or turns.

Facebook Twitter Pinterest South Korean professional Go player Lee Sedol, right, prepares for his second stone against Google’s artificial intelligence program, AlphaGo. Photograph: Lee Jin-man/AP

Computers had already conquered chess, when in 1997 IBM’s Deep Blue defeated world champion Garry Kasparov. Go was “the only game left above chess”, as DeepMind’s CEO Demis Hassabis put it before Wednesday’s showdown.

Lee, a South Korean who sports a bowlish haircut and looks younger than his 33 years, spent much of the match leaning forward, cradling his chin in his hand. Sat opposite him was DeepMind developer Aja Huang, who physically placed the stones on the board in positions chosen by AlphaGo. Lee played aggressively from the outset, putting AlphaGo on the defensive.

There are more possible Go positions than there are atoms in the universe DeepMind’s CEO Demis Hassabis

The match was close, with both AlphaGo and Lee making mistakes, but eventually Lee conceded that AlphaGo had built an insurmountable lead. AI had scored a victory in one of the most creative and complex games ever devised.

Lee maintained a meek posture in a post-game press conference, hanging his head and at times looking to be on the verge of tears. He expressed surprise at his opponent’s strong performance. “I didn’t know AlphaGo would play such a perfect game,” he said.



Facebook Twitter Pinterest Go player Lee Sedol at the press conference after losing to AlphaGo. Photograph: Lee Jin-man/AP

The result shocked many Go aficionados. As recently as two weeks ago, Lee said he was confident of a sweeping victory. AlphaGo’s defeat of a European Go champion in October last year – an achievement many thought was at least a decade away – should have acted as a warning.

AlphaGo’s mastery of Go is so significant because of the near-infinite number of board positions available and the intuition that top human players rely upon to pick between them. Hassabis described Go as “the most elegant game that humans have ever invented”, with “simple rules [that] give rise to endless complexity”.



“There are more possible Go positions than there are atoms in the universe,” he added.

DeepMind’s team built “reinforcement learning” into the programme, meaning the machine played against itself and adjusted its own neural networks based on trial and error. AlphaGo is capable of narrowing down the search space for the next best move from the near-infinite to something more manageable. It can also anticipate long-term results of each move and predict the winner.

The match took place in a quiet room as reporters watched on a projector screen from a separate press area. The game, including commentary, was live-streamed on YouTube.

AlphaGo doesn’t get tired, doesn’t forget, doesn’t worry Andrew Okun, president of the American Go Association

Ben Lockhart, a 22-year-old who took up Go as a child in New York and who moved to South Korea four years ago to study the game full time, welcomed the unprecedented level of attention brought by the AlphaGo contest. “That no one really knows this game [in the west] has been frustrating for a long time. At least after this more people will have heard of Go,” he said.



Maybe part of the reason that the game has struggled to make inroads in the west, where it has no history, is that it is a less than scintillating spectator activity. The action inches along, with long pauses as players eye the board and contemplate their next move. It isn’t always obvious to viewers unfamiliar with the game who is winning. After a couple of hours of play, most reporters were slouched in their chairs playing with their smartphones.



Lee has four more chances to beat AlphaGo and claim the $1m in prize money. The stress and fatigue affecting the South Korean won’t be a problem for his opponent when they reconvene for game two on Thursday 10 March.

“Historically, Go has been a game of people testing themselves against each other, and themselves. It has been a game of character,” Andrew Okun, president of the American Go Association, who flew to Seoul to watch the showdown. AlphaGo, he added, “doesn’t get tired, doesn’t forget, doesn’t worry”.