Strange things happen at the one-two point

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    Keywords: Tactics, Proverb

The 2-1 points have some peculiarities; and the heuristic principles of fighting, which normally apply to the sides, often work differently in the corner.

One reason is the impossibility of approaching a 2-1 point from the corner side. This can give the player who occupies the 2-1 point an additional tempo to win a capturing race.

[Diagram]

Usual way to fight a capturing race

In this case Black wins.

[Diagram]

Take the 2-1 point first

White wins.

Here Black cannot attack from either side because of shortage of liberties.


tderz: From WeiQi the predecessor of WeiQi TianDi, 1980, Nr. 4, p.31 and, of course, some other famous sources..

In all problems Black has sente.

[Diagram]

Problem 1

/Problem 1 Attempts
/Problem 1 Solution?

[Diagram]

Problem 2

/Problem 2 Attempts?
/Problem 2 Solution?

[Diagram]

Problem 3

/Problem 3 Attempts
/Problem 3 Solution?

[Diagram]

Problem 4

/Problem 4 Attempts?
/Problem 4 Solution?

[Diagram]

Problem 5

/Problem 5 Attempts?
/Problem 5 Solution?

[Diagram]

Problem 6

/Problem 6 Attempts?
/Problem 6 Solution?


Another feature of the 2-1 point is the possibity of a throw in tesuji. An example is considered at Stupid Moves.

I will show another example.

[Diagram]

White 2 was a small mistake

Black played B1 as a ko-threat. I will not discuss whether this was the best threat. White answered at W2 giving Black another threat at a. White should have played at a.

[Diagram]

A direct atari

Here WC was in answer to BC. In fact it also attacks BC; and is a direct threat.

The throw-in W1, at the 2-1 point, captures BC, because of the weakness at a.

Actually I can point to a stupid player with White who lost a ko because of this mistake. It was a certain HolIgor (IGS 5k*).

Thank you for correcting mistakes.


The 2-1 point is a place where many kos happen. For example, the ko that HolIgor (IGS 5k*) lost.

[Diagram]

Black starts ko

Black plays B1 hoping for White's mistake. White sees the ko. White suspect that she wins the capturing race without ko (but it is so difficult to read 8 moves ahead, shame on her!), and she decides to fight the ko.

But the sad story of White's mistake has little to do with the topic, and the topic of this page is the 2-1 point. By taking it, Black got a ko that saved his group.


How is this a capturing race? After black's play at the 1-2, wouldn't white make life by:

[Diagram]

White makes life

or

[Diagram]

Guess there's a disadvantageous ko here...

-- Malweth


The 2-1 point is a critical point in many life and death problems. The difference between living or dying locally is at least 20 points. It is something that cannot be taken easily. That's the difference between winning and losing, or losing and losing badly.

Examples

See also:


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This is a copy of the living page "Strange things happen at the one-two point" at Sensei's Library.
(OC) 2007 the Authors, published under the OpenContent License V1.0.
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