The first round of the 36th WAGC saw Poland’s Koichiro Habu 4d miss a critical move that could have allowed him to snatch victory from Canadian Juyong Koh 7d, both playing for their first time at this event. Given their ranks, the clear favourite going into the game was the Canadian 35-year-old insurance broker, who succeeded to reach a good position by the end of the fuseki (click here for the sgf file). But it was in the middlegame where Habu had a moment’s chance to reverse the game and score his first win in the tournament.
In Diagram 1, White (Koh) cuts at move 76 in an attempt to counterattack Black (Habu) and rescue the marked stones. In the game Black answered with the natural-looking nobi at 1 in Diagram 2, however this was a fatal mistake. The game continued until move 8, where Black was confronted by a dilemma. B is the vital point for Black to kill White, however if White manages to play at A the game is over, as the ladder is good for him.
Instead of the nobi at 1, Black should first atari at A. If White plays as in Diagram 3, this time the ladder is good for Black (the stone at A is a ladder breaker) and this could have won the game for Habu. In the actual game however it was Black whose stones were cut off and captured.
– Ranka, based on commentary by Michael Redmond 9p.