Capturing Race (Semeai) in Go: When Two Groups Fight for Air
⏱ Read ~6 min · Updated July 2026 · Part of: Learn Go
A capturing race (Japanese: semeai, 對殺) is Go's most tense moment: two enemy groups, neither with eyes, fighting over the same outside liberties. Whoever runs out of liberties first is captured. Count right, and you know who lives.
| English | 中文 | Plain meaning |
|---|---|---|
| capturing race | 對殺 | two eyeless groups fight for liberties |
| semeai | 對殺（日） | the Japanese term for the same thing |
| liberty | 氣 | empty points next to a stone |
| shared liberty | 共享氣 | an empty point touching both groups |
| eye | 眼 | a surrounded empty point (ends the race) |
1. What a capturing race is
Two groups are adjacent. Neither can make two eyes, so neither is safe. The only question: who has more liberties, and who can drive the other to zero first?
🥊 Analogy: two wrestlers locked in a room with one air vent. They're not trying to open a window for themselves — they're trying to plug the other's vent. The first to suffocate loses.
2. The race position (recognize this shape)
Two enemy groups pressed together, no eyes between them, sharing a ring of outside liberties:
Black group ((0,1)(1,0)) and white group ((0,2)(1,1)) are in a race. Whoever has more outside liberties — whoever can fill the other's liberties first — wins.
3. The basic count
Count each group's liberties (empty points touching it but not shared with the enemy).
- Black's liberties: (0,0) empty + ... count the whole group's outer empty points.
- White's liberties: same, count the whole group's outer empty points.
The one with more liberties usually wins — they can afford the one-for-one exchange (you fill one of mine, I fill one of yours) and still have liberties left.
🎯 Simple rule: if I have more liberties than you and neither side can make an eye, I win this race. If both sides have the same number of liberties, the side that moves first loses (because you fill one of theirs, they fill one of yours, and you hit zero first). This is "equal liberties, first-move disadvantage."
4. Shared liberties and eyes make it complex
Real races have two complications:
- Shared liberties — empty points touching both groups. Shared liberties usually help the side already ahead (mathematically they count toward the side with more outside liberties), but in mixed cases you must count carefully.
- Making an eye during the race — if one side makes a single eye during the fight, their advantage jumps. Because an eye is an "unfillable liberty" — the opponent can't touch it until all your outside liberties are gone. So "eye kills no-eye" (有眼殺無眼 — the side with an eye almost always wins the race).
Strong players read races several moves ahead, watching for the moment to make or destroy an eye — this is advanced life and death.
5. Capturing race vs seki
Sometimes a race ends in seki (雙活) — neither side can capture the other, so both live in a frozen draw. This happens when shared liberties make it so that "whoever moves first gets captured" (if you fill a shared liberty, the opponent fills your last liberty).
Recognizing "this race is actually seki" saves wasted moves — don't spend moves fighting a race you can't win.
6. The 4 most common race mistakes for beginners
- Acting without counting. The outcome of a race is 100% determined by liberty counts. Not counting, acting on feel, is blind fighting. Count both sides' liberties first, then decide attack or defense.
- Moving first when liberties are equal. Equal liberties = first-move disadvantage (you hit zero first). When equal, don't start the fight — wait for the opponent, or find sente elsewhere (ko threats / forcing moves) before coming back.
- Ignoring eye-making. Making one eye during a race almost guarantees a win (eye kills no-eye). When you see a chance to make an eye, grab it — don't only focus on filling the opponent's liberties.
- Not recognizing seki. Some races can't be won (shared liberties create seki). Fighting on = wasted moves. Recognize seki, stop, redirect elsewhere.
7. Capturing races on the 4×4 board
The small board produces short, sharp races where liberty counting is out loud. Many 4×4 capture puzzles are, underneath, one-move races: find the move that puts the opponent in atari while keeping your own group safe. Count first, then move — this is the foundation the brainGO engine verifies for every puzzle.
How to train it
Counting liberties under pressure is a skill — train it with short puzzles and instant feedback.
👉 Play brainGO — win your first capturing race
FAQ
How do you count who wins a capturing race?
Count each side's outside liberties (not shared). More liberties wins. If equal, the side that moves first loses (hits zero first). With shared liberties, calculate carefully (they favor the side with more outside liberties). If one side makes an eye, they almost certainly win (eye kills no-eye).
What should I do when liberties are equal?
Don't start the fight — equal liberties means first-move disadvantage. Either wait for the opponent to move, or find sente elsewhere (forcing moves / ko threats) to reduce the opponent's outside liberties first, making your count effectively higher, then come back.
What does "eye kills no-eye" mean?
In a race, the side that makes one eye almost always wins. Because an eye is an "unfillable liberty" — the opponent can't touch it until all your outside liberties are gone. So having an eye is like having a liberty the opponent can never fill.
How do you tell a capturing race from seki?
A race is when one side can capture the other (more liberties wins). Seki is when neither can capture (shared liberties make "whoever moves first gets captured"), resulting in both living. Recognizing "a race I can't win = seki" saves wasted moves.
Related guides
- Learn Go: the visual beginner's guide — the beginner hub (this article's home)
- Liberty — what you count in a race
- Capture — the outcome of a race
- The eye · Alive and dead — making eyes ends races
- Seki (mutual life) — when a race becomes a draw
- Atari — the alarm during a race