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Lee Sedol

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Lee Sedol is a legendary former professional Go player from South Korea. He held the prestigious 9 dan rank, which is a high level of expertise in the game. Throughout his career, he earned 18 international titles. This achievement places him second only to Lee Chang-ho, who holds 21 titles. Because of his incredible skill, many people called him "The Strong Stone" (Ssen-dol). He was a master of the game of Go, a strategy game played with black and white stones on a board.

Lee's career was defined by his ability to use unexpected strategies. In April 2003, during the KAT cup, he played a match against Hong Chang-sik. Lee used a formation known as a broken ladder. In professional Go, a broken ladder is usually considered a mistake. It typically leaves the chasing stones weak and leads to a loss. However, Lee played black and used this formation to capture a large group of Hong's stones. This move brought his own stones back to life in the corner. His opponent eventually resigned the game.

Lee's path to greatness began early in his life. He was born in 1983 on Bigeumdo Island in South Korea. He studied his craft at the Korea Baduk Association. At age 12 years and 4 months, he became a professional Go player. This made him the fifth-youngest professional in South Korean history. He officially entered the professional ranks as a 1 dan in 1995. By 2003, he had rapidly ascended to the 9 dan rank. During that same year, he won both the 7th LG Cup and the 16th Fujitsu Cup.

In March 2016, Lee participated in a historic series of matches. He played against AlphaGo, an artificial intelligence program. AlphaGo was developed by Google DeepMind, a firm based in London. The five-game match was broadcast live and carried a $1 million prize. Lee entered the match with great confidence. He even suggested he could win by a score of 5–0 or 4–1. He accepted the challenge in only five minutes. The match tested the limits of human skill against machine intelligence.

The match against AlphaGo was a rollercoaster of emotions. Lee lost the first three games by resignation. However, the fourth game became a masterpiece in Go history. Lee played white and made a move at White 78. This move was called a "brilliant tesuji," which is a clever tactical play. Another expert, Gu Li, called it a "divine move" because it was so unforeseen. This single win brought Lee immense joy. He later said he would never exchange that specific win for anything in the world.

Despite that brilliant victory, the overall match ended with a score of 1–4. Lee lost the fifth game while playing black. This loss had a deep impact on his view of the game. He felt that the dominance of artificial intelligence made it impossible to be the top player. He described the experience of losing to AI as his "entire world collapsing." Because he could no longer enjoy the game, he announced his retirement in November 2019. He called AI an entity that cannot be defeated.

Even after retiring from professional play, Lee continued to engage with the technology. In December 2019, he played a three-game match against the HanDol AI system. This system was developed by the Korean NHN Entertainment Corporation. Lee played with a two-stone handicap in the first and third games. He won the first game against the machine. However, HanDol won the next two games, resulting in a 2–1 victory for the AI. Lee's career remains a vital chapter in the relationship between human creativity and machine logic.

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