Capture Race in Go — How Semeai Liberty Counting Works | PlayGo.gg

A position where two groups of opposing colors share liberties and do not have 2 eyes.

What is a capture race?

A capture race — semeai in Japanese, 수상전 in Korean — happens when two opposing groups are pressed against each other with no room for either to make two eyes. Neither group can live on its own, so survival depends on capturing the enemy first. Whichever side runs out of liberties first dies.

Capture races appear constantly in real games: a corner invasion that gets cut off, two cutting stones tangled with each other, or a deep reduction that can't quite settle.

When to use capture-race counting?

Any time two enemy groups are touching and neither has two eyes, you're in a capture race — and the move you "feel like" playing matters less than the count. Three rules govern the math:

- Outside liberties are normal — count them straight. - Shared liberties (points adjacent to both groups) get filled last and effectively belong to whoever has more outside liberties. - An eye is a liberty the opponent cannot fill. A group with one eye beats a group without one even when raw liberty counts look even — the proverb is me ari me nashi, "one with an eye, one without."

The order of moves is strict: outside liberties first, shared liberties next, atari and capture last. The single most common mistake is filling a shared liberty too early and self-ataring your own group.

Example of a capture race in a game

Where should black go to win this capture race?

Capture races are all about reading ahead. If you can count the liberties properly, you can decide whether or not to start a fight or leave it for ko threats!