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Problem: On which point must black place a stone in order to capture white and remove the unit from the board?

Dia. 17

Answer:
C. It may help to think of a liberty as a breathing space. Without a breathing space stones smother and die. A black stone on point C produces the folowing position:

Dia. 18

Black now has 1 white prisoner.

Dia. 19

Answer:
C.

Dia. 20

Answer:
A and B. In this example, two liberties would have to be filled before the white stone could be removed.

Dia. 21

Answer:
A. The following diagram shows the position after black plays at A. Notice that the capture opened new liberties for the black units.

Dia. 22

Black now has 3 white prisoners.

Whenever connected stones lose their last liberty, they are all captured.

No matter how many stones in a unit, the more liberties it has the stronger and safer it is. In Diagram 22, black gained liberties by capturing white. The other way for a unit to gain liberties is by Problem: On which point can white play to increase the number of liberties for his nearly enclosed units below? (Hint: Count the liberties before and after an added stone).

Dia. 23

Answer:
B. White has one liberty now; a white stone at B will result in three liberties for white, one at A, one at D, and one at C.

Dia. 24

Answer:
A. White has one liberty at A; a white stone added at A will result in three liberties for white, points B, F, and E.

Dia. 25

Answer:
B. Adding a white stone at B will increase the white liberties from two to four. Confirm that a white stone on D will not increase the number of white liberties.

This one is trickier; count carefully.

Dia. 26

Answer:
B increases the count from four liberties to five.

Dia. 27

Answer:
None of these points will increase the number of white liberties.

Players often extend in order to avoid capture. The added stone itself may reach to new liberties, as in the preceeding diagrams, or the new stone may connect the unit to another unit.

Problem: On which point can black play in order to rescue the five-stone black unit, below?

Dia. 28

Answer:
Black's endagered unit will be saved, and strengthen to four liberties (and gain access to even more), if black joins his stones by playing at point C.

Whenever a unit has only one liberty remaining, it is in atari (ah tah ree).

Problem: Look again at each of the preceding six diagrams. In which of them are there stones in atari?

Answer:
Diagrams 23, 24, and 28.

A player who has just had a unit put into atari is not required to try and protect that unit. Neither is the other side ever required to capture. Stones may remain in atari indefinitely.

As you begin to play go, it is instructive and courteous to warn your opponent as soon as a unit comes into atari. Atari is to go as check is to chess. Saying "atari" means: "As it stands, I can capture that unit on my next play."

Race to Capture

In each game, the players spend much of the time trying to arrange escape for friendly stones and trying to prevent the escape of enemy stones. Points that lie under captured stones are the territory of the captor. Therefore the question of capture or escape is vitally important.

Problem: Where will black play in the following situation?

Dia. 29

Answer:
Black will fill the last liberty of the white stones in the corner and remove them from the board, simultaneously opening new liberties for the endangered black stones.

Dia. 30

Black now has five white prisoners

If white gets the first play, white will take black's last liberty, capturing black and saving the cornered white stones.

Dia. 31

White now has six black prisoners.

Chapter Two

Life and Death

In this chapter we will examine safe enclosures and some enclosures that are unsafe.

Safe and Secure

In go, the players always seek to encircle territory, often the same territory at the same time. Sooner or later opposing stones meet and begin to push against each other. Liberties appear and disappear with each play. The conscientious player keeps track of the security of each unit involved in a battle.

Since stones are captured when opposing stones occupy all their liberties, then it follows that stones cannot be captured if the enemy stones cannot occupy all their liberties. Stones with safe liberties always have these liberties surrounded. Therefore safe liberties must lie inside an enclosure.

Problem: Can black occupy all the white liberties in each of the three diagrams below?

Dia. 1

Answer:
Yes. White has failed to surround territory and thus has no safe liberties here.

Dia. 2

Answer:
No. White has succeeded in surrounding territory. Imagine that black begins to place stones inside this white enclosure. Notice that the invading black stones will always run out of liberties before white does. Therefore white cannot be captured.

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