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Two liberties
Path: GiveMeLiberties · Prev: Liberty · Next: ShortageOfLiberties
Difficulty: Introductory
Keywords: Tactics
In my games, I've noticed that nearly as important as atari is when a group has just two liberties. What kind of liberties they are determines whether they're safe. When a group has just two liberties, unless both are eyes, it is one move away from being in Atari. In all of the below discussion, I assume that the groups don't have two eyes. Make sure that your group can be saved, even if either liberty is taken. Basic Example
This group has two liberties, a in the northwest and b in the south.
Black can defend an attack from the northwest...
... but not from the south. The black stones die, because if Black tries to escape with
More ExamplesThree examples are inspired by my own games:
The
After
W moves at
Black loses eight pieces, because he lacks liberties.
Ladders and NetsMany situations are related to having just two liberties.
In a ladder, an attacker repeatedly reduces a group of stones from two liberties to one liberty.
A simple net keeps the number of liberties to two or less. White has two liberties. If white moves to either a position, black will reduce white's liberties by moving to the nearest b position.
Double atari
A double atari can occur when two groups with just two liberties share a liberty that's not an eye.
Ko threats
Every group with just two liberties (not both eyes) can be used as a ko threat.
Auto-atari
Auto-atari can only happen when your group had two liberties, you move into one liberty, and you gain no more liberties. In this diagram, I chased after
... that I hadn't counted my liberties.
Same shape, different order.
A snapback is a specific kind of auto-atari. See also: Alex Weldon: Even three is not enough, quite often.
Here, White can be captured in geta with a Black move at a. In fact, see Five liberties for tactical stability. Path: GiveMeLiberties · Prev: Liberty · Next: ShortageOfLiberties This is a copy of the living page "Two liberties" at Sensei's Library. ![]() |