Miai (version 26)

Paths: <= Endgame => · <= Good Play =>

Difficulty: Advanced Keywords: Go term

The term mi-ai denotes that a player has two different options to his or her disposal. For example, in this diagram white lives because if black plays at a, white plays at a; 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.

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.

Usually, it is better not to play in 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 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.

This diagram comes from KanazawaProblemOne?. When white - mistakenly - plays 1, she makes an eye at the circled points. It is obvious that she can make a second eye at A if she would be able to play at 2. So black plays at 2 in order to prevent that. This is quite an obvious move for black.

If white plays - mistakenly - at 1 here, the right spot for black to kill her does not jump to the eye as easily as in the previous diagram. All 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 Black 1 - we might assume 1 and D to be miai, and answer white 1 with black D :

At this stage it is again obvious that, if white plays A, black plays B. So if white plays B first, ...

... black answers at 4 - again using miai reasoning. The shape is a BentFourInTheCorner and white is dead.

Miai is indeed great for players with poor reading abilities like me :o) I don't know if creating miai points in local positions can be considered as a (nameless) tesuji, but here is a small example I've found in a chinese tsumego book :

The goal for B is to separate white stones. Obviously, this would generate a big profit for B (territory in the corner and prisoners). How ?

B 1 is the suji making respectively miai of A and B for connecting the marked stone to the upper black group, and miai of C and D for cutting.

Of course, just like the example at the top of this page, these points aren't strictly equivalent, since both players now want A and C in order to minimize loss/maximize profit. But IMHO, this keeps being a detail compared to the change in the local status.

Granted, this example doesn't add very much to the topic, but it shows the use of miai for attacking in a not so basic position. So I thought it might be useful :-)

--Nando