By Nam Chi-hyung
When you are walking to the opposite corner of a city block, it's possible to get there by first going straight and then turning right, or going right first and then turning to the left. As long as you reach your destination, everything is fine. However, in Baduk, playing A first and then B is completely different from playing B first, then A.
To play Black 1 and 3 right away can be good endgame moves, but will not save the five ¡a-marked black stones. After the five stones are in atari, it is useless for Black to cut A and give atari to White since his stones will die before White's. However, if Black changes the sequence slightly, they can be saved.
Cutting with Black 1 is a move called sequential magic, which revives the five stones in danger. Owing to the exchange of Black 1 and White 2, now White cannot connect at A against Black's atari with 7.
Sometimes the change in the order of moves can make the opponent play a move contrary to his own benefit.
White's group on the left side is in danger. The good thing for White is that there are several cutting points in Black's shape. The desperate series of atari and cutting, however, cannot save the group.
To cut at 1 first is the sequential magic in this case. Because of the double-atari with A, Black cannot help but play an empty triangle with 2. If Black plays A to avoid the double-atari, then the one black stone in the corner will be killed by White B.
Continuing from the last diagram, White 5 is a good move to make the capturing race favorable for White. After Black 6, White no longer has a reason to give atari with A, so plays 7 instead. If Black connects at A, Black's group in the corner, rather than White's, will die.
This is a problem for finding the best endgame move to reduce Black's territory to the left. White can give atari either with A or with B. However, simply playing atari with either of the two doesn't have big reducing power.
White 1 here is a brilliant move to enlarge the power of White's atari. The position on the lower side and White 1 are worth remembering. This is a way to make the atari, which is usually a very simple move, much more powerful. If Black blocks White's connection with 2, then the atari, white 3, becomes more powerful, forcing Black to compose an empty triangle with 4. After worsening Black's shape like this, White can bridge under with the sacrifice of White 3.
If Black answers against White 1 from above as here, White will give atari from underneath with 3, which again forces Black to make an empty triangle and then connect White 1 with 5.
The writer is a baduk professor at Myongji University and a professional player of the game.