Lee Sedol vs AlphaGo (Google Deepmind): The Historic Match Between Human and AI


Baduk is a board game played in a 19×19 grid board. It is played with black and white stones, with the black playing first. White is automatically awarded extra points (handicap),  different in Korea and Japan, and China, for playing second.

Are you aware of a game called Baduk [Bah-dook], widely known as Go? I will refer to this game as Baduk(바둑), which is how it is called in Korea. Baduk is a board game played mostly in the Eastern Asian countries Korea, Japan and China, and is quite unknown to Westerners. I would not be surprised if most of you have never heard of this game before. So who cares about some obscure Asian board game? The game has been a huge issue recently due to the ongoing five-game match between Lee Sedol, a Korean Baduk legend, and AlphaGo. Who is AlphaGo? AlphaGo is not an actual person. AlphaGo is a computer program developed by the Google Deepmind team in England. This match is considered to be a historic battle of skill between artificial intelligence (AI) and human.

What is Baduk (Go)?

Baduk is a simple yet complex game. The goal of the game is to occupy more total area of the board than the opponent. It originated in China, and ultimately reached Japan through Korea. It is played most in Korea, Japan and China, but the rules are slightly different between the three countries. Baduk was considered to be a game that AI would have difficulties in overcoming their human counterparts due to its complexity. Its large branching factor meant that it would be hard for a computer to consider all possibilities to find the best move in a limited amount of time. Baduk is a game with high variability, with an estimated 10761 possible number of games. In comparison, chess  is estimated to have 10120 possible games. A computer program called Deepblue, developed by  IBM, has already beaten chess World Champion Garry Kasparov in 1997. However, computer programs had not yet beaten professional human Baduk players without handicap.

The rise of AlphaGo

AlphaGo first caught attention in October 2015, when it first beat a professional Baduk player in 2015. Fan Hui is a 2dan professional, and the current European champion. It is important to note that the skill level of professional Baduk players are rated in a dan system, like some martial arts, and the highest possible dan is the 9dan. Fan Hui lost all five games in the five-game match with AlphaGo. The uniqueness of AlphaGo derives from the fact that it can continously “learn,” and can analyze previous matches of Baduk between human opponents. Due to this reason, AlphaGo continues to improve as time passes. As mentioned previously, no computer program has ever beaten a professional Baduk player without handicap. Many professional players in traditional Baduk strongholds, such as Korea, Japan and China, downplayed this achievement. Many questioned the skill level of Fan Hui, since he is “only” a 2dan professional. The skill difference between a 2dan and a 9dan is quite significant. In hypothetical matches between Lee Sedol and Fan Hui, Lee Sedol is expected to win almost all of the time.


Korean Baduk Legend Lee Sedol

Lee Sedol

Lee Sedol is a famous Korean Baduk player, and is ranked at 9 dan. He is considered to be one of the best Baduk players ever, and entered professional level at the young age of 12. Currently 33 years old, many agree that he has left his best years behind him, and is declining. However, he is still one of the top Baduk players in the world. Lee Sedol is currently ranked fourth based on world ELO rankings, and second in Korea by the Korean Baduk association. Looking at his overall career, he is considered to be one of the legends of Baduk not only in Korea, but in the world as well. Although Lee Sedol’s decline suggests that he is not the best Baduk player based on current form, Google Deepmind team felt his overall legendary status in the game made him the worthy opponent for this historic match. As of now, China’s 9dan Ke Jie is ranked first based on world ELO rankings. However, Lee Sedol’s has one of the most illustrious career among Baduk professionals, in which Ke Jie has yet to catch up to.

Lee Sedol vs AlphaGo

AlphaGo is a computer program, and it is therefore unable to set the Baduk stones by itself. Aja Huang, a programmer part of the Deepmind team, will set the stones and take part in the black/white selection process for AlphaGo. The historic Baduk battle between Lee and AlphaGo has gained attention not only in Korea, but worldwide. It gained immense interest from the Korean media and public, and also caught the attention of Baduk fans in China and Japan as well. Many Korean, Chinese and Japanese professional Baduk players expressed their support for Lee Sedol. Most professionals think that Lee would achieve a sweeping victory over the AI counterpart. The match gained international attention, and the results of every match was reported by media outlets worldwide.




Lee Sedol (Black) plays the first move in the first match against AlphaGo (White) played by Aja Huang (Deepmind Programmer). 



Lee Sedol (Black) vs AlphaGo (White) Match 1: March 9 (KST)

Result: AlphaGo Win by resignation

Prior to the beginning of the matches, Lee Sedol was confident that he would easily win against AlphaGo. He described it as a “matter of winning 5-0 or 4-1.” The vast majority of Korean 9 dan professionals, the Korean public, Baduk fans around the world, and China’s Ke Jie agreed. However, Lee Sedol’s stance changed a day before match 1, in which he was cautious of how much AlphaGo has improved since the October 2015 matches against Fan Hui. In the first match against AlphaGo, Lee had a shaky start. Lee started to gain momentum as the game progressed towards the mid-game, and the commentator for Korea’s BadukTV felt that Lee had the sight upper-hand in a very close game. Michael Redmond, the only 9dan Westerner who is also the commentator for the English commentary live on Youtube, remarked that the game was a close one from the mid-game towards the end of the game, and was not sure who would win. But, the match ended abruptly when Lee Sedol made a deliberately illegal move to show his intention to resign. A resignation towards the end of the game is common in Baduk, since professional players can accurately measure their own points as well as the opponent’s points to judge the game progress and determine if they would almost certainly lose. At this point of the game, it would be practically impossible to win unless the opponent commits a grave mistake, which is quite egregious. The result came as a huge shock to Lee Sedol, and he seemed to be immensely shaken by his loss. The Korean Baduk community, and the Korean public, was stunned as this unexpected result. Many, including Lee Sedol himself, did not expect to lose. Lee Sedol, in his post-game interview, admit his shock at AlphaGo’s immense skill. He also admitted that he “did not expect to lose,” and expressed his “deep respect for the programmers of AlphaGo.” This was in response to Demis Hassabis’, CEO of Google Deepmind, expression of respect towards Lee. The Korean media and public perceived that Lee Sedol was quite nervous in this game, and many thought that Lee was not able to fully show off his skills. Many Korean commentators and fans felt that Lee he had made several detrimental mistakes that led to his own loss. As such, many fans were hopeful that Lee would win the second match.

Lee Sedol (White) vs AlphaGo (Black) Match 2: March 10 (KST)

Result: AlphaGo Win by resignation

Following his defeat the day before, Lee Sedol played more cautiously. AlphaGo played moves described by Korean commentators as “anomalies.” Korean commentators felt that AlphaGo “does not play like a human.” Lee Sedol started off much better this time, and many Korean 9dan professionals thought that he did not make any noteworthy mistakes throughout the whole game. However, this game also ended as a loss for Lee Sedol, as he resigned to admit his defeat in this game as well. There were times when Korean commentators thought that AlphaGo made a mistake, but many turned out to be good moves after the game has progressed. Scary, since it seemed that AlphaGo was able to predict the game at a very early stage. This game was critical in establishing AlphaGo’s skill of the game, as many felt that Lee Sedol played well despite playing slightly more cautiously than his normal self. This game established AlphaGo’s skill, as Lee did not commit any notable mistakes. Due to this reason, Korean commentators felt that this was the game that AlphaGo beat Lee Sedol purely due to its superiority in skill, as opposed to Lee Sedol breaking down through his own mistakes in the first match. As a result, it the position as the challenger seemed to have transitioned from AlphaGo to Lee Sedol.

Lee Sedol (Black) vs AlphaGo (White) Match 3: March 12 (KST)

Result: AlphaGo Win by resignation

Korean commentators were remarking that Lee Sedol is playing an “aggressive style of Baduk” that is reminiscent of the style of play when he was younger. Lee Sedol has lost the match again, despite having a very interesting match.

Lee Sedol (Black) vs AlphaGo (White) Match 4: March 13 (KST)

Result: Lee Sedol Win by resignation

Lee Sedol was quite underwhelming in the beginning. However, the 76th move by was hailed as many Baduk professionals as “the move of God.” AlphaGo realized its mistake too, and played erratic moves that seem to reveal some bugs of AlphaGo. Demis Hassabis tweeted too about how brilliant the move was, and how AlphaGo’s calculation of its probability winning plummeted after this move.


Pop-up window shown by AlphaGo after losing to Lee Sedol. 

Lee Sedol (Black) vs AlphaGo (White) Match 5: March 15 (KST)

Lee Sedol in the post-match press conference, remarked about AlphaGo’s weaknesses. He thought that AlphaGo was slightly weaker when playing black, and also that when the opponent plays an unpredicted move, there seem to be “bug-like mistakes” by AlphaGo. Therefore, although the black/white selection was to be made randomly on the day of the match, Lee Sedol specifically requested the Google Deepmind team to  allow him to play black, as he had already won against AlphaGo as white. Although it was a hard fought match, where AlphaGo used up its two hour allocated time for the first time, Lee Sedol surrendered to AlphaGo.

Result: AlphaGo Win by resignation



The five match game between Lee Sedol and AlphaGo had gained immense interest worldwide. Game results were reported by major news outlets, giving Google’s Deepmind team huge publicity. Lee Sedol also became a sensation in Korea, and despite his name being previous known, became even more famous. The public sympathized with his losses, and celebrated his wins.  People were cheering him on through his matches, reflected by the media’s overwhelming coverage of the matches. Additionally, interest for Baduk surged again in Korea. Although there had been some interest due to the famous Korean drama “Reply 1988,” in which the main character played by Park Bo-Gum was a professional Baduk player, the influence of Lee Sedol and AlphaGo was unmatched. This likely also had a part in the immense public interest, especially from women, of the Baduk match.  Live stream of the matches was watched by tens of thousands of people in Korea, and the worldwide stream operated by Deepmind via Youtube also enjoyed a large number of viewers. People began parodying the name of “AlphaGo,” and Saturday Night Live Korea also aired a segment regarding this match. Overall, it seems to be a huge success for not only AlphaGo and the Deepmind team, but for Lee Sedol as well.


As the members of the public, it seems that we have watched a part of history unfold, and the beginning of something. Could this signal the rapid development of Artificial Intelligence? The applications for this powerful technology seem to be endless, and while some are excited about the positive outlook, there are others fearful for the consequences these types of technology may bring.


Lee Sedol vs AlphaGo

Where? Four Seasons Hotel in Seoul, South Korea
Who? Lee Sedol and AlphaGo (Google Deepmind)
When? March 9, 10, 12, 13, 15
Match 1: AlphaGo
Match 2: AlphaGo
Match 3: AlphaGo
Match 4: Lee Sedol
Match 5: AlphaGo

5 replies »

  1. Yey! I used to learn Baduk when I was really young and it is very good for your concentration. I believe this match gives a lot of messages to world :) Thank you for sharing this great story!

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