In this article we will present the notion of potential, or aji in Japanese. Aji is an abstract concept used to describe a position on the goban. It is not uncommon to hear players kibitzing and saying, "Um, there's aji there! "to designate a position where there is something possible...
Determine if there is aji in a position is based on two things:
For the first, practising tsumegos is essential, for the seconde, tesujis and looking at professional games to learn new techniques is great but to practise both, playing a lot of games is the key. In this article, we will highlight the difference between "good" and "bad" aji.
A position where there is no (or little) aji is called "good" aji. That is to say, no move (twisted or not) is possible later in such position. Otherwise, it is called "bad" aji. We will see here two examples, one simple to explain the principle of aji and one more complicated from a professionals game.
Let's look at the next diagram:
White has invaded black's corner, and black is solid on the outside and has a good influence. In this position, it is said that black has good "aji" because its position is very solid and there is no real weakness that white can exploit. Let's now look at diagram 2 below:
Here, due to the position of the marked white stone, the black position is much weaker than before. Indeed, under good circumstances, white can take out its stone in atari and destroy the black position. This involves a shicho. If white comes out, we find the continuation of the shicho in the diagram below:
If the shicho is good for white, it's a disaster for black! So in this position, until black has captured the white stone, he will have to constantly pay attention to the shicho! Isn't that awful?
We also see in diagram 4 that the geta with black 3 does not work. After 3, A and B are miai: both save the white stones while capturing black stones.
Thus, a difference of a single stone can turn a positionwith "good" aji to one with "bad" aji.
Here is a position of a game between Lee Changho 9p (black) and Park Yeonghun 9p (white), two Korean professionals, played in 2013 on the occasion of the 8th Siptan. Siptan was the equivalent of the Japanese Judan title: it was a fast Korean tournament where each player had an initial time of 10 minutes and a byo yomi of 5 periods of 40 seconds. This tournament, born in 2005/2006, was stopped in 2014.
In the game, Black has just invaded the top side with 1, and White pushes black with 2 to force him to make an extension of two intervals with 3. White then plays 4, which is an aggressive move to attack the life base of the two Black stones while protecting the corner. Against this move, 5 is a tesuji! Indeed, if White wants to continue attacking black, he must play 6, Black responds lightly in 7 and 9.
But why is move 5 so interesting?
The first impression is that the Black exchange 5 for White 6 weakens the two black stones on the side, and this is the case. But here, Black is in the white sphere of influence because White is solid on both sides. Black must therefore manage his group in a light way, it is why he answers in 7 and 9.
After this sequence, stone 5 makes bad aji in the White corner. Let's look at diagram 2:
It's the same game, but a few moves later. Black played stones on the right side, which allow to "reactivate" stone 5 of diagram 1 in the White corner. Thanks to the exchange 10, 11 and 12, if White does not protect in A directly, Black can himself go down to A to connect his stone and destroy the White corner. Let's now look at diagram 3:
Here, it is the same position as the previous diagram, but the Black A exchanges for White B was not made. When Black exchange 1 for 2 and then returns in 3, this time against the Black move in C, White can choose to go down and keep his corner. So we see that here, because of the fact that there is no longer the Black stone in A, this exchange of moves (1, 2 and 3) is less severe against White's corner. The presence of stone in A is therefore essential in this situation!
But one of the difficulties in using aji is timing: it is important to use the aji of a position, or to make an exchange of moves creating aji in a position at the right time.
Let's go back to diagram 4 above. This time, against the White 1 move, Black makes a tobi to get his group out and White consolidates his corner with the 2 move. At that moment, if Black plays move 3, White can answer solidly in 4. Note the difference with the position studied previously: this time, the aji in the corner is limited!
Here therefore, playing the Black move 4 one move too late makes that there is much less bad aji in the white position. Timing is therefore crucial! In a future article, we will look in more depth at the notion of aji by analyzing positions in professional games.