30 December 2015

A Zugzwang Lesson

It is not stalemate if a pawn can move.

The last game to finish in today's Holiday Tournament offered an illustration of a lesson from yesterday's Holiday Chess Camp. The two-day camp had three groups--beginners, intermediate, and advanced. One of the youth coaches who was in the advanced section yesterday reached an ending today that he might have understood better had he been in the room with the intermediate players yesterday. It was a youth chess camp, but coaches were encouraged to join the young players in the advanced camp, which was taught by FM Jim Maki.

John Dill and I taught the intermediate group.

Our Holiday Tournament had a scholastic section (NWSRS Rated) that I ran, and a USCF rated open section run by Dill. The Open section was one-third youth and two-thirds adults. The last game to finish was on board one, where a coach had White against a parent of one of the co-winners of the scholastic section.

White to move

I had been watching the game for several moves before I took a photo with my phone, which helped me to reconstruct this position. My sense was that the game was a draw. Black offered a draw here or a couple of moves later, explaining to his opponent that even without the Black pawns on the board, White could not win.

Indeed, White's bishop cannot help the h-pawns to promote because it cannot control the promotion square.

While the players were discussing the draw offer, John Dill whispered to me, "it's the position that we showed the children yesterday." I looked again with a new set of eyes. John was correct. White wins this position with correct play.

The player of Black is correct that without his pawns, White cannot win. However, those pawns change everything. If Black's king cannot move, then the g-pawn must advance.

In John's lecture, "Finding the Best Plan in the Endgame," he presented this position, which he found in Ray Cheng, Practical Chess Exercises: 600 Lessons from Tactics to Strategy (2007).

Black to move

There are obvious stalemate dangers, but if Black prevents the White king from moving without restricting the b-pawn, then White will be in zugzwang.

1...Bc2 2.Ka2 Bb1+ 3.Ka1 Kc2 and White is forced to play b3 or b4.

Both moves lead to 4...axb3 (or cxb3) and after White's only legal move, 5...b2#.

In the tournament game this afternoon, the presence of Black's pawns were fatal to his position. His opponent, however, did not find the winning idea. The bishop must go to g8 and trap the king on h8. Compelling Black's g-pawn to move produces checkmate in two moves.

John and I were both enthusiastic that a position from our camp instruction appeared in an important tournament game the next day.

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