Cho Chikun loses Honinbo titleAfter holding the Honinbo
title for a record 10 consecutive terms, Cho Chikun finally went
down in defeat at the hands of 29-year-old Cho Sonjin. The new
champion was a dark horse from the beginning in the league that
determines the challenger for the title. His career up to now has
not been particularly illustrious, although he has won three titles
reserved for younger players. Most observers predicted that he would
be lucky to win even one game against Cho Chikun. But after
splitting the first four games of the best-of-seven match, Cho
Sonjin got the measure of the former Honinbo and won the next two
games and the title by a score of 4-2.
In the
crucial sixth game, Cho Chikun was in overtime: he had used up his
allotted eight hours and had to make each of his moves within one
minute. This situation is normal for Cho in two-day games. He was
clearly winning, but the pressure of time and the realization that
he would lose the title if he did not win this game probably caused
him to make an uncharacteristic blunder.
The final position is shown in Figure 1. A capturing race
had developed between the marked black and white stones in the upper
right. Cho Chikun (white) could have easily started a ko to capture
the six marked black stones, but he descended to White 1. When Black
also descended to 2, it was clear that the white stones would die,
so Cho Chikun resigned.
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12, 18: played 7; 15, 21:
at9 | If White had played 1
in Diagram 1, the sequence would have continued to White 5.
If Black captured with 6, White would atari with 7 in Diagram
2. Black would play 8, putting the White group into atari, so
White would capture the ko with 9. Black would then have to threaten
to increase the liberties of his embattled stones with 10 and 16 as
ko threats, but White 13 and 19 are huge ko threats that Black
cannot ignore. After White takes the ko with 21, Black has no
significant ko threats, so he will lose nine stone in the top right
when White plays at A. Moreover, Black would now have to play at B
to make two eyes for his group on the left.
In spite of this loss, Cho Chikun still holds the top two
Japanese titles--the Kisei and the Meijin--so by anybody's reckoning
he is still number one in Japan. Therefore, he could still be upbeat
about this result. He promised to be back next year as the
challenger and repeat his feat of holding the Honinbo title for 10
straight terms.
Answers to last week's problem In
Problem 1, White has an eye on the second line at the top, so
if Black is going to kill the white stones, he has to destroy the
white's eye shape below. Black 1 in Diagram 3 fails to
accomplish this because White will answer with 2. Although Black has
created a false eye at A, White gets his second eye at B, so his
stones are alive.
White 2 in Diagram 3 is clearly the key point because if
White can play there he gets two eyes. Therefore, Black must play on
1 himself as in Diagram 4. White plays 2 to stop Black 1 from
linking up to his stones on the outside, but Black now plays 3,
putting a white stone in atari. White will capture with 4, but Black
throws in a stone at 5 in Diagram 5. White can capture this
stone, but that point is a false eye. White will eventually have to
play there, so he is left with only one eye and his stones are dead.
In Problem 2, White has to make a
second eye at the top if he is going to live. A placement at 1 in
Diagram 6 is the key point. White plays 2 to stop Black from
linking up to his stones on the left, but Black pushes in at 3,
sacrificing two stones. After White captures with 4, Black throws in
a stone at 5 in Diagram 7 leaving White with a false eye at
the top. White's stones are now dead.
You might think that Black 1 in Diagram 8 would force
White to connect at A, then Black can play 2 destroying the eye at
the top. However, White will answer Black 1with 2. White can now
fight a ko. If he is able to win the ko by connecting at A, he will
have his second eye to the right of 2. Clearly, it would be better
to kill white cleanly by playing the sequence in Diagrams 6
and 7.
In the
position in Problem 3, the only move that will kill the white
stones is for Black to throw in a stone at 1 in Diagram 9.
White cannot play at A because he puts his stones into atari.
Therefore, he makes an eye in the corner with 2 in Diagram
10. Next, Black ataris with 3 and 5, and the eye at 1 is now a
false one, so White is dead.
If White captures Black 1 with 2 in Diagram 11, Black will
play 3. If White next plays A, Black will play B, leaving the white
stones with only one eye (at 1). If White B, Black plays A and the
eye at 1 is a false one. Either way, White's stones are dead.
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