AlphaGo defeated world champion Lee Sedol in the ancient Chinese board game Go.
Developed by Google DeepMind, AlphaGo used a combination of neural networks and tree-search methods to evaluate positions and select moves. Its 2016 match against Lee Sedol in Seoul ended with AlphaGo winning four games to one.
The result was a major milestone because Go has an enormous number of possible positions, making brute-force calculation far harder than in chess. AlphaGo’s success showed that machine-learning systems could develop strong strategies in a game long considered especially difficult for computers.
AlphaGo is often confused with Deep Blue, IBM’s chess computer that defeated Garry Kasparov in 1997. Watson is another IBM system, famous for quiz-show performance rather than Go. AlphaGo’s match also helped popularize the strategic move known as “Move 37,” which surprised professional players.