Serieshelpstalemate December 30, 2008
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The next puzzle involves a type of problem which I believe has never been featured in ChessBase Christmas puzzles before. Therefore I will give an example first to explain how it works.

Serieshelpstalemate in eleven

This problem (by Günter Glass, Serienzug-Rekorde 1980) is a serieshelpstalemate in 11, which means that Black plays 11 consecutive moves (without White moving at all) in order to reach a position in which White can give stalemate by playing one move. Both sides are cooperating to bring about the stalemate. There is one further rule, which is that Black is not allowed to give check except possibly on the last of his sequence of moves.

Pins are usually very important in serieshelpstalemates and he we can reasonably guess that in the final position a black piece will be pinned on the a8-h1 diagonal. Since White can make at most one capture during the solution, this means that in the final position there must be either three of four black units on the board (not counting the king).

It seems likely that Black’s king will remain on h1 (or there cannot be a pin), so something must guard or block g1. It is easy to see that a black piece on g1 will always have a move, so this means that White’s final move must be Kf2 or Kxf2. Then we can guess that a black piece must be on g2 (which must be a knight), blocking in another black piece on h2 (which must be a rook). To reach this position isn’t difficult: 1.e1R (not 1.e1N and 2.Ng2, as this blocks the rook’s route to h2) 2.Re2 3.Rh2 4.e2 5.e1N 6.Ng2 (unpinning the d5-pawn) 7.d4 8.d3 9.d2 10.d1N (to reach f2 in time) 11.Nf2 and now Kxf2 stalemate.

Black is stalemated

After this brief lesson in the art of serieshelpstalemate here is our sixth Christmas puzzle:

Serieshelpstalemate in eleven

There are a lot more pieces on the board, but this puzzle is no more difficult to solve than the one above; indeed, if you spot the idea quickly, then you may find it easier. As a hint, remember what I said about pins!

Problems selected and annotated by John Nunn.
The solutions to all puzzles will be published at the end of the series (after January 1st).
Please do not send in solutions after each problem is published.