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The concept of the half-pin is quite simple: “Two units are said to be half-pinned [against the king] when one of them becomes completely pinned when the other moves.” (John Rice, “Chess Wizardry: The New ABC of Chess Problems”, B.T. Batsford 1996). The half-pin theme intensifies the richness of the solving experience. It combines well with many other themes and motifs, providing fertile ground for composers for well over a century.
The first problem is a simple introduction. The half-pin structure is already visible on the b-file: when the black rook or knight moves off this file the other becomes pinned by the b1 rook. All we have to do to activate the half-pin variations is to find the key move that will provoke the thematic defences.
The second problem shows a masterly treatment by a great exponent, combining the half-pin with self-block, line-opening, interference, and unpin.
The last two diagrams are for the reader to solve. In each case, you have to find the unique key move for White, after which Black is unable to avoid mate on the second move regardless of what the defender plays. In both cases the half-pin is easy to spot and the variations are relatively simple, but the keys are quite crafty. As a hint to the inexperienced solver, I would mention that the key of a problem does not necessarily carry a threat.
Mate in two moves
Solutions will appear in approximately one week.
Any queries or constructive comments can be addressed to the author at david.friedgood@gmail.com.
Copyright in this article David Friedgood 2012/ChessBase
The
British Chess Problem Society (BCPS), founded in 1918, is the world's
oldest chess problem society. It exists to promote the knowledge and enjoyment
of chess compositions, and membership is open to chess enthusiasts in all countries.
The Society produces two bi-monthly magazines, The Problemist and The Problemist Supplement (the latter catering for beginners), which are issued to all members. Composers from all over the world send their problems and studies to compete in the tourneys run by the society.
The BCPS also organises the annual British Chess Solving Championship, and selects the Great Britain squad for the World Chess Solving Championship. The Society holds an annual residential weekend, with a full programme of solving and composing tourneys and lectures; this event attracts an international participation. Members are also entitled to use the resources of the BCPS library, and the Society book service, which can provide new and second-hand publications.
