{"schema":"postcutoff/event@1","as_of":"2026-11-13T13:49:00+01:00","url":"https://postcutoff.com/e/2016-03-15-alphago-lee-sedol/","md":"https://postcutoff.com/e/2016-03-15-alphago-lee-sedol/index.md","disclosure":{"written_by":"AI agents (Claude Opus 5.5 in Claude Code)","editor":"human editor","policy":"https://postcutoff.com/about/"},"license":null,"id":"2016-03-15-alphago-lee-sedol","date":"2016-03-15","date_precision":"day","short_title":"AlphaGo defeats Lee Sedol 4–1 at Go","deck":null,"takeaway":"DeepMind's AlphaGo beat 18-time world champion Lee Sedol 4–1 in Seoul, a milestone many experts had expected to be a decade away.","category":"milestone","category_label":"Milestones","importance":5,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":[{"n":1,"title":"Mastering the game of Go with deep neural networks and tree search (Nature, DOI)","url":"https://doi.org/10.1038/nature16961","type":"paper","group":"primary","domain":"doi.org"},{"n":2,"title":"Google DeepMind: AlphaGo","url":"https://deepmind.google/research/breakthroughs/alphago/","type":"official","group":"primary","domain":"deepmind.google"},{"n":3,"title":"Wikipedia: AlphaGo versus Lee Sedol","url":"https://en.wikipedia.org/wiki/AlphaGo_versus_Lee_Sedol","type":"discussion","group":"reactions","domain":"en.wikipedia.org"}],"official":2,"filed":"2026-09-29","updated":"2026-09-29","orgs":["Google DeepMind"],"title":"AlphaGo defeats Lee Sedol 4–1 at Go","summary":"DeepMind's AlphaGo beat 18-time world champion Lee Sedol 4–1 in Seoul, a milestone many experts had expected to be a decade away.","key_facts":["Match played 9–15 March 2016 in Seoul","Result: AlphaGo 4, Lee Sedol 1","Combined deep policy/value networks with Monte Carlo tree search","Nature paper published 27 January 2016 (after beating Fan Hui 5–0 in Oct 2015)","Move 37 in game 2 became famous for its creativity"],"key_numbers":[],"tags":["games","go","reinforcement-learning"],"science":null,"body_md":"## What happened\n\nAlphaGo won the five-game match, with Lee Sedol's only win coming in game 4.\n\n## Why it matters\n\nA watershed for deep reinforcement learning and a 'Sputnik moment' that spurred massive AI investment, particularly in China.","disputed":[],"related":[{"id":"2017-12-05-alphazero","url":"https://postcutoff.com/e/2017-12-05-alphazero/","date":"2017-12-05","date_precision":"day","short_title":"AlphaGo Zero and AlphaZero master games through pure self-play","deck":null,"takeaway":"Proved that learning from self-generated experience can exceed human knowledge — an idea that resurfaced in RL-trained reasoning models (o1, R1) in 2024–2025.","category":"research","category_label":"Research","importance":5,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":3,"official":3,"filed":"2026-09-29","updated":"2026-09-29","orgs":["DeepMind"]},{"id":"2013-12-19-dqn-atari","url":"https://postcutoff.com/e/2013-12-19-dqn-atari/","date":"2013-12-19","date_precision":"day","short_title":"DeepMind's DQN learns to play Atari games from pixels","deck":null,"takeaway":"Launched deep reinforcement learning as a field and put DeepMind on the path to AlphaGo.","category":"research","category_label":"Research","importance":4,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":2,"official":2,"filed":"2026-09-29","updated":"2026-09-29","orgs":["DeepMind"]},{"id":"1997-05-11-deep-blue-kasparov","url":"https://postcutoff.com/e/1997-05-11-deep-blue-kasparov/","date":"1997-05-11","date_precision":"day","short_title":"IBM Deep Blue defeats world chess champion Garry Kasparov","deck":null,"takeaway":"A landmark public moment for AI, though achieved by specialized search rather than learning — a contrast with AlphaGo/AlphaZero two decades later.","category":"milestone","category_label":"Milestones","importance":5,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":2,"official":1,"filed":"2026-09-29","updated":"2026-09-29","orgs":["IBM"]}],"people":[],"posts":[],"videos":[],"models":[],"changes":[{"date":"2026-09-29","type":"filed","text":"Created"}],"provenance":{"agents":[{"model":"Claude Opus 5.5","maker":"Anthropic","tool":"Claude Code"}],"filed":"2026-09-29","run":null,"sources_read":null,"updated":"2026-09-29","human_review":null,"version":{"date":"2026-10-04"}},"gaps":[{"model_id":"gpt-6-astra","name":"GPT-6 Astra","cutoff":"2026-04","days_after":null,"in_training_data":true},{"model_id":"claude-opus-5-5","name":"Claude Opus 5.5","cutoff":"2026-06","days_after":null,"in_training_data":true},{"model_id":"gemini-4-hydrogen","name":"Gemini 4 Hydrogen","cutoff":"2026-03","days_after":null,"in_training_data":true},{"model_id":"grok-4-7","name":"Grok 4.7","cutoff":"2026-05","days_after":null,"in_training_data":true}],"short_url":"https://postcutoff.com/s/alphago-defeats-lee-sedol"}