Walkie Talkie Seven

    Keywords: Life & Death
[Diagram]
Walkie Talkie Seven  

In this shape, the point cross is the vital point. A Black play there (or at any of the other internal points except the point a) leads to 6 points of Black territory.

If black has two or fewer outside liberties, which is likely given the shape, then White can turn this shape into a throw-in ko or a seki. With more outside liberties, White cannot achieve anything.



Table of contents Table of diagrams
Walkie Talkie Seven
Main line
Two choices for White (B4 = [tenuki])
Seki (B6 = tenuki)
Playing out the ko: Part 1 (B4 and B6 = tenuki)
Playing out the ko: Part 2 (B12 and B14 = tenuki)
Ten thousand year ko
Seki (B6 and B8 = tenuki, W7 connects at B4)
Playing out the ko: Part 1 (B8 takes ko at B4)
Playing out the ko: Part 2 (B12 and B14 = tenuki)
Playing out the ko: Part 1 (B8 takes ko at B4)
Playing out the ko: Part 2 (W11 takes ko, B14 takes ko at BC)
Variation for B2
White can't capture
Variation A: Black lives
Variation B: Black still lives

Two or fewer outside liberties

[Diagram]
Main line  

If white takes the vital point with W1, Black's best response is at B2 (but see later what happens if black plays B2 at W3).

After W3, Black will not want to play at b because this move reduces the eyeshape to a pyramid four, thus killing the group in gote. Playing at either c or d is also bad, as White would reduce the eyeshape to a bent four in the corner via a move at a.

Thus, Black only has two options in this position:

  • Playing elsewhere, which gives White the choice of either making a seki or starting a throw-in ko; or



Black plays elsewhere with B4

#toc4 #toc3
[Diagram]
Two choices for White (B4 = tenuki)  

If Black plays B4 elsewhere, White has two choices for playing locally: making a seki with a, or playing the approach move at either c or d to prepare for a throw-in ko.



1. White makes a seki

[Diagram]
Seki (B6 = tenuki)  

When neither side has enough ko threats, the simplest variation for White after Black plays B4 elsewhere is to make a seki with W5. However, because this move is not urgent and removes the possibility for a ko (see aji keshi), White should normally wait until the end of the game to play it.



2. White makes a throw-in ko

[Diagram]
Playing out the ko: Part 1 (B4 and B6 = tenuki)  

If White has more ko threats than Black does, White may capture the corner via a throw-in ko. However, it requires one extra ko threat and allows Black to play two additional moves elsewhere relative to the seki variation shown above.

Whether this exchange is worth the cost would depend on the rest of the board. If the trade is not profitable to White, it is usually better to leave the position alone after W3 as shown earlier and wait until later to decide whether to start a ko or to make a seki.

[Diagram]
Playing out the ko: Part 2 (B12 and B14 = tenuki)  



Black makes a ten thousand year ko with B4

[Diagram]
Ten thousand year ko  

If Black plays B4 as shown, White will most likely play elsewhere or capture the ko by playing W5 at b.



3. White makes seki

[Diagram]
Seki (B6 and B8 = tenuki, W7 connects at B4)  

White may make a seki at any time by connecting at B4. As in the case Variation #1, this is more likely to occur if neither side has enough ko threats.



4. White captures the corner

[Diagram]
Playing out the ko: Part 1 (B8 takes ko at B4)  

If White has one more ko threat than Black does, the corner can be captured. As in the case of Variation #2, White only needs one more ko threat than Black does to win the ko.

[Diagram]
Playing out the ko: Part 2 (B12 and B14 = tenuki)  

Notice that Black gets one fewer move elsewhere in exchange of the corner in this variation when compared with Variation #2 (where Black plays B4 elsewhere rather than making the ten thousand year ko). However, this variation is not necessarily inferior, as the alternative of playing B4 elsewhere earlier gives White the choice of what to do in the corner:

  • If White is komaster, White can wait until the endgame to start the throw-in ko. By then, Black would gain very little in exchange for the corner through the extra move elsewhere.
  • If the ko is fightable for Black, White could simply choose the seki variation to deny Black the chance to live with points. If Black wishes to delay White's timing for making a seki and possibly live with points in the corner, making the ten-thousand-year ko is the only way to do so.



5. Black lives with points

[Diagram]
Playing out the ko: Part 1 (B8 takes ko at B4)  

If Black has two more large ko threats than White does, this variation may be played to live with points in the corner. However, White will get two moves elsewhere in the exchange.

Since Black has much less to gain from settling the corner immediately than White does, this exchange is unlikely to be profitable in most situations. Therefore, Black would most likely wait until the endgame before committing to playing out the sequence starting with B10 even if he does have enough large ko threats.

[Diagram]
Playing out the ko: Part 2 (W11 takes ko, B14 takes ko at black+circle)  



Variation for B2

[Diagram]
Variation for B2  

This way the position becomes a direct ko, which is an inferior result for Black because he will get less compensation in exchange for the corner if he loses the ko (two moves elsewhere, compared to 3 or 4 in the above-mentioned variations). White can finish the ko by filling at W2; it would be a mistake to play one of the other inside liberties instead.



Special case: Three or more outside liberties

[Diagram]
White can't capture  

Although the situation shown here is perhaps unlikely to occur in real games, it is of theoretical importance. If Black's group has three or more external liberties, White cannot achieve anything yet, as Black can set up an oshitsubushi as shown in the following two variations. However, White can use the corner as a source of ko threats if Black has exactly 3 external liberties.

[Diagram]
Variation A: Black lives  

Notice the importance of the third outside liberty: without it, B8 would not be possible.

[Diagram]

Variation B: Black still lives


See also:


Walkie Talkie Seven last edited by MrTenuki on July 29, 2011 - 22:33
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