7. Fluid and Undefined Positions
Don't Erase Aji!

by Richard Bozulich

When comparing professional games to amateur games, something you often notice is how frequently a pro will stop in the middle of a joseki, or even in the middle of a fight, and play elsewhere. Often the reason is that they want to avoid eliminating the aji — or the latent possibilities — that exist in a position.

Here is an example from a recent professional game.

Highlight Diagram
Highlight Diagram
White is quite thick on the top left, so the extension along the top with the marked stone seems quite natural. This move also attacks the weak underside of Black's corner enclosure on the right.

Dia. 1
Dia. 1. Attach-and-Extend
Black attached with 1 and extended to 3. His aim was to build a wall facing down the right side, press White against the top, making him overconcentrated, and stake out a large-scale moyo on the right side. After exchanging 4 for Black 5, White invaded with 6 to prevent Black from securing his moyo.

Dia. 2
Dia. 2. Sacrificing two stones
Black took this opportunity to create some aji by cutting with 7 and descending to 9, intending to sacrifice two stones.

After White 10, how should Black continue?

Dia. 3
Dia. 3. Overconcenrated
The usual moves are to force with the atari of 1, then make White capture two stones with 3 and 5. Black's wall is solid with no defects, so he can attack the white stone on the right side with 7.

As for White, his stones at the top are overconcentrated; that is, the number of stones White has invested is not worth the amount of territory he has secured.

There is, however, one problem. At this stage of the game White might not answer Black 3. Instead, he might simply play a big move elsewhere. If Black makes good on his threat by playing at 4, White could play another big move. Therefore, it is important to make sure that your forcing moves are big enough to be really forcing. Certainly, Black 1 here is very forceful.

So how did Black continue?

Dia. 4
Dia. 4. Exploiting the aji
Without playing the forcing moves in Dia. 3, Black attacked the white stone with 11 and left the position at the top undefined. If White now runs away with 'a', Black can play a knight's move at 'b', threatening to capture the marked stone in a ladder, starting at 'c'. If White defends against this threat with a move around 'c', Black can continue his attack at 'd'.

Dia. 5
Dia. 5. Attacking with a cap
After White jumps to 1, Black might first peep at 2, then directly attack with a cap at 4. Let's assume White fights back with an attachment at 5. Next —

Dia. 6
Dia. 6. Double atari
Black hanes at 6 and White cuts at 7. A series of ataris now follows, culminating in a double atari on three stones at the top and three below. Whichever group of three stones White decides to give up, it will not be good for him.

This is just one example of how White's bad aji at the top can help Black counter any invasion into his moyo below.

Figure 1 (1–46)
Figure 1 (1–46)
Here are the moves that led up to the position in the highlight diagram. They were played in the 32nd Ryusei tournament between Yokotsuka Riki 7-dan (Black) and Wu Hoyi 5-dan on May 15, 2023.

Figure 2 (47–69)
Figure 2 (47–69)
When Black played 57 (Black 11 in Dia. 4), White immediately eliminated his bad aji at the top with 58.

After White extended to 68, Black played a nose-attachment tesuji at 69, attacking two white stones.

Figure 3 (70–79)
White 78 connects at the marked stone.
Figure 3 (70–79)
The nose attachment in Figure 2 led to a squeeze with the moves to 78. White picked up a couple of stones, but didn't make much progress in the fight below. After Black connected with 79, White was left with three weak stones stranded inside Black's vast moyo.

205 moves.
Black won by resignation.

The move-by-move game record can be found at: Yokutsuka versus Wu

Recommended reading
To read more on the topics of aji and fluid and open positions, I recommend Essential Go Proverbs. In particular, the following sections:
    Atari, atari — the sign of duffer go, page 45
    Beware of playing forcing moves, page 464
    Keep your options open, page 467