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Miai
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  Difficulty: Intermediate   Keywords: Tactics

Definition of miai

[Diagram]
Miai

The term mi-ai denotes that a player has two different options at his or her disposal.



For example, in this diagram White lives because if Black plays at a, White plays at b; and if Black plays at b, White plays at a, in both cases making two eyes.

We say that a and b are miai for two eyes. In general any such situation where when one player takes or prevents one of two options, the opponent will play the other, is called miai. In English, the points are sometimes said to reflect each other. (Think of a see-saw.)

This might be the case in a local position like this, but also in more general, strategic concepts. For example, if Black has a large moyo which White can reduce or invade from two sides, the two invasions might be miai. For another good example of miai, see wariuchi.

Note that equivalence is an important aspect of miai. In miai positions, both the points are about the same in value, but they may not be exactly the same.

Usually, it is better not to play out miai points without additional reason. For example, in the situation above, a black move at a or b is sente. But playing it in the middle game is a loss of a ko threat which might prove to be decisive for the outcome of the game.


Miai as a tool for problem solving

Example 1

Miai is not only an observation, something nice-to-know. Miai can be an effective tool when looking for a move. One cannot assume thoughtlessly that two moves are miai, but doing so can lead to the right move, and reduce the amount of thinking over a problem.

[Diagram]
Miai

This diagram comes from Kanazawa Problem 1.



When White plays W1 (mistakenly), an eye is created at the circled points. It is obvious that White could make a second eye at a if White was able to play at B2.

So Black plays at B2 in order to prevent that. This is quite an obvious move for Black.

[Diagram]
Miai

If White plays at W1 here (mistakenly), the right place for Black to kill does not jump to the eye as easily as in the previous diagram.



Each of a, b, c and d deserve several seconds of thought... unless one thinks of the concept of miai.

If we think of the previous diagram - where White d was answered by B1 - we might assume W1 and d to be miai, and answer W1 with Black d:

[Diagram]
Miai

At this stage it is again obvious that, if White plays a, Black plays b.



So if White plays b first...

[Diagram]
Miai

... Black answers at B4 - again using miai reasoning.



The shape is a bent four in the corner and White is dead.


Example 2

Miai is indeed great for players with poor reading abilities. Here is a small example found in a Chinese tsumego book:

[Diagram]
Black's best move?

The goal for Black is to separate white stones.



Obviously, this would generate a big profit for Black (territory in the corner and prisoners). How?

[Diagram]
Double miai

B1 is the suji making respectively miai of a and b for connecting BC to the upper black group, and miai of c and d for cutting.



Of course, these points aren't strictly equivalent, since both players now want a and c in order to minimize loss/maximize profit. This is a mere detail compared to what is at stake.

But it does provide an "additional reason" for playing it out. If played out correctly, each player will get one play of a miai pair.

In this example, because it will be White's turn, we expect that White will seize a and c, leaving b and d for Black.
This is a useful example that shows the use of miai for attacking in a not-so-basic position.


See also:


Contributors:

This page was Wiki Master Edited by unkx80 from the old page.



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This is a copy of the living page "Miai" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.