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Eyes, life and death · Lesson 22

Capturing races: whose liberties run out first?

When two groups surround each other and each must capture the other to survive, a capturing race may arise. Count liberties while also checking the actual order of play.

An empty point next to only one side is an outside liberty; one next to both is shared. Filling a shared liberty may reduce your own liberties too. In the initial diagram, C2 and D2 are shared: whoever plays C2 first leaves their own group with only D2.

Some liberties need a preparatory move to fill; groups may have eyes, gain liberties by capturing or create ko. “More liberties wins” works only in simple cases and cannot replace reading move by move. The next lesson uses this shared-liberty example to explain seki.

Two shared liberties

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Lower-left corner: Black C1 and D1 and the eight surrounding white stones share only C2 and D2 as liberties. The separate outer black group has eyes at D5 and F5 and serves as a stable boundary.

Black fills first

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After Black fills C2 first, the inner black and white groups each have only D2 as a liberty. White to play.

Black plays first and is captured

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White at D2 captures Black C1, D1 and C2. Black lost by filling the shared liberty first.

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