Lesson 3: Capturing and Saving Groups
The move that causes the opponentâ€™s group to be reduced to only 1 liberty is known as atari. It means that, if the opponent does not respond to this move, his group can be removed from the board during the next move.
In Diagram 3-1, the white move at 1 is known as atari. Since at the next white turn white can play at 2 to remove the black stone, black can save (to prevent capture) his stone by playing at 2 so that the 2 black stones have now 3 liberties. Note that when under atari, you should always save your stones by playing at where your opponent would play to remove your stones.
If not, like Diagram 3-2, black 2 is a wrong move, resulting in white 3 removing the black stone from the board. In Diagram 3-3, black 1 is ataris the five white stones, and black can play at 2 at his next turn to remove the white group. White 2 is the correct move for saving his group.
3.2. Surrounding Groups
To capture a group, you always need to surround the group completely.
In Diagram 3-4, white 1 causes the black group to be totally surrounded, effectively killing the black group. If it is blackâ€™s turn, black should save his group by playing at 1 in Diagram 3-5.
Similarly, in Diagram 3-6, black will play at 1 to block whiteâ€™s only exit route to capture the white group. In Diagram 3-7, white should break out from the surrounding black stones by playing at 1 in order to save the white group.
3.3. Creating and Destroying Eyes
When a group is completely surrounded, you may be able to save it by creating at least two eyes. On the other hand, to capture a group, you need to surround it totally and also to prevent it from creating two eyes.
Diagram 3-8 shows that for white to prevent his group from being killed, he needs to play at 1 to create his second eye. Now his group is safe. If it is blackâ€™s turn instead, black will also play at 1 in Diagram 3-9, leaving white with a lone eye, capturing the white group.
Consider the black group in Diagram 3-10. Playing at black 1 gives black three eyes for ensuring that the black group is saved. Likewise, in Diagram 3-11, white will play at 1 so that black has only one real eye (together with three false eyes), capturing the black group.
3.4. Saving Groups by Using Defects in Surrounding Stones
Sometimes, the stones surrounding a group have some inherent weaknesses, or defects. The defects may be used to save the surrounded group.
In Diagram 3-12, it seems that white is dead with totally no chance of living. But white can play at 1, removing the three black stones from the board and hence save his group. (Of course, if it is blackâ€™s turn, he should play at A to remove the four white stones from the board.)
In Diagram 3-13, black has totally surrounded the four white stones at the corner and white has no eyes at all. However, white can atari at 1 and making an eye at the same time, forcing black to save his two stones at 2, and white makes the second eye at 3. If black 2 plays at 3 to destroy the second eye, then white will play at 2, capturing the two black stones.
Let us take a look at Diagram 3-14. There is some obvious defect in the white group. Black can atari the triangle white stone at 1, and at the same time threatening to break out from the surrounding white stones. If white 2 chooses to complete the surrounding barrier, then black 3 captures the white triangle stone and forms two eyes. If white chooses to save his triangle stone by playing at 2 in Diagram 3-15, then black breaks out of the surrounding white group by playing at 3. However, atari at 1 in Diagram 3-16 is a wrong move, white responds at 2 and the black group is dead.
End of Lesson 3
Some Tournament Conventions
If the Go tournament rules and regulations do not specify otherwise, the following conventions are usually applied by default:
-The tournament will be played on 19×19 boards, which is the most widely used board.
– Before the commencement of the game, the player holding the white stones will grab a handful of white stones and asks the opponent to guess whether the number of stones in the hand is odd or even. If the opponent guesses correctly, then the opponent will choose the colour; else the player holding the stones will choose the colour.
– Clocks are commonly found in Go tournaments just like Chess tournaments to limit the amount of time a player has for a game. In fact, the clocks used in Go tournaments and Chess tournaments are identical. When it is your turn your time will run but your opponent’s time will not. Likewise if it is your opponent’s turn his time will run but not yours. Hence it is possible to limit the time to say, 1½ hours per player. If a player uses up all his time, then he loses the game.
– To start the game, the white player will press the clock. A player will press the clock after making his move. Note that if you remove your opponent’s stones from the board as a result of your move, you will press the clock only after you have finished removing all his stones from the board.
– Latecomers will have their time penalized by the amount of time they are late and if they are late by a stipulated amount of time (say ½ hour), then they loses the game automatically (or by default, using tournament terms).
– During the commencement of a round or a game, the players and the bystanders should not talk, give comments or hints or distract other players. Bystanders should also avoid standing too near the players.
– Any disputes during a game should be referred to the organizing committee and the judges’ decision is final.