British Go Journal No. 67. April 1986. Page 19.

Interpolis Match – Game 1

In September of last year a unique match took place between Europe's two strongest players. Yong-Su Yoo is a 32 year old Korean, ...[details omitted]. Ronald Schlemper is Dutch, aged 27, the present European champion ...[details omitted].

The match was organised and handsomely sponsored by Interpolis, a Dutch insurance company with an admirable record of supporting what the Dutch call 'denksporten'.

[Discussion omitted.]

Black: Ronald Schlemper
White: Yong-Su Yoo
Komi: 6
The game-file in Ishi and SGF format.

Figure 1 (1-50)

• White 10: Schlemper expected this move at 41. But Yoo felt that if Black plays next at 15, white 16, black 17, white 18*, then he has invested too many stones at the top, especially since black can also play a forcing move at 13.
  *BGJ had white 4 which is impossible. 18 assumed.
• Black 15: The 15 and 17 combination are 'kikashi' – forcing moves which, here, strengthen black's position temporarily. If white plays 31 black can defend flexibly in a ko by playing A.
• White 22: A mistake, according to Yoo, because after 22-29 white must defend in gote with 30, since the ladder after a black cut at B is unfavourable. Black thus gets the big point of 31 first. Instead Yoo recommends white 24, black 29, white 25, black 27. The likely continuation is then white 31, black C (safest given white's strength below), white D, black 49, white 32.
• White 32: Important both territorially and because it revives the 'aji' (latent potential) in 8.
• Black 35: A mistake. This invasion is large, but white builds central thickness and gets sente to take the last big point at 46.
• White 44: Ideal timing. Black must submit with 45 because of white's strong wall. If he tries to resist with 1 in Dia 1 he loses the fight.
• Black 47: A small mistake. This move is 'aji keshi' – erasing one's own potential. Black loses the chance to play 48 himself.
• White 50: The follow-up to 32; the stone can connect to either 8 or 32.

Diagram 1

Dia 1. If black resists with 1, white sets up a semeai which he wins by one move. Note that white 16 is necessary otherwise black cuts there and wins the fight.

Figure 2 (51-100)

• Black 53: A standard way of invading white's moyo, but a serious blunder of omission. Black should first force with 60, white A for reasons which will become apparent.
• Black 55: Also aji keshi; Black loses ko threats and the chance to play 56.
• White 58: Descending to B leaves too much bad potential in the corner. For example a black stone at C is virtually sente because of the possibility of D.
• White 60 exploits black's^* failure to play here. Black is on the spot. He can hardly connect at 1 in Dia 2, since after 2-5 the two marked stones have become completely redundant, and later A-D overconcentrates black still further. But 61 leaves some very nasty aji in black's position that Yoo skilfully exploits.
  * BGJ had "white's".
• White 64: 'Attack with keima' says the proverb.
• Black 65: A standard 'tesuji' in this position to extricate one's stones and well worth learning. If White replies with 1 in Dia 3, black breaks out in the sequence to 10.
• Black 69: May have been better at 70. The semeai in Dia 4 leaves black two liberties ahead, although white may have other options. Black now has great problems looking after his weak group because of all the forcing moves white can make at the top.
• Black 77-83: Best, but white can start a large ko in the corner (with E).
• Black 89: The losing move. It eliminates the ko, but the bottom group now falls under a fatal attack. Black must defend at 91, white will start the ko, but black can take a large point such as F in compensation, and the game would still be close.
• Black 91: The only chance now is to play at 94, but after white 91, black loses half his group and white will end with sente to play on the lower side.

Diagram 2

Diagram 3

Diagram 4

Figure 4 (101-180)

• White 91-114: White's attack has put him clearly in the lead. 114 is actually bad – he should extend to 115. But Yoo seems to have counted that this capture, together with the large yose at 118 and 128, is enought to win.
• Black 141: A last desperate attempt to get something from an attack on white's top group. But ...
• White 160: ... White easily refutes it.

White wins by resignation after 180.

Game 2 is on page 22.