## Monday, March 31, 2008

### Themes

When a composer of chess problems decides to create a new problem, he/she usually desires to present a new idea or a known idea in a new form.
The idea behind a problem is called theme of the problem.
The theme adds logic, coherence and beauty to a problem.

The themes have various objectives. There are ...
___(a) themes related with moves before the key, (in the set play and in the virtual play),
___(b) themes related with the key itself,
___(c) themes presented during the phase after the key (in the actual play), as they are the “line closures”, the “line openings”, the “special arrangements” of pieces, the specific “squares where the lines of action of the pieces intercept” (we call these squares “intersections”), the “interferences” that are created, και
___(d) themes which span over various phases of the solution of the problem and observe how the defenses of black and the mates of white are changing.

When the solver of chess problems tries to solve a problem, basically he/she seeks to discover the idea that is hidden by the composer in the problem and to appreciate how beautifully and economically this goal has been achieved.
The solver must examine the play in every phase of the problem and to ascertain that the mates are changed from one phase to the next.
The solver must not be led astray by the tries (attempts of the white refuted by a unique move of the black) and must find the the unique key and the main variations after the key.

In order to clarify the expression "a theme is contained in a problem", we shall see the Indian theme. It was called Indian because the reverend Loveday was in India when he first presented it. From the description of the theme we understand that it needs at least three moves to be completed.

 Theme Indian : A ”critical” white piece makes a ”critical” move and passes over a ”critical” square. Then a white piece self-interferes on the critical square to avoid stalemate of the black and in the next move withdraws giving check by discovering of the critical piece.

 (Problem 127) Rev. Henry Augustin Loveday, “The Chess Player Chronicle”, 02/1842 White plays and mates in 3 moves #3 (4+3) [ 8/4p3/7B/4p3/4k1P1/8/5K2/3R4]

Key: 1.Bc1! (The critical piece Bf6 makes the critical move to pass over the critical square d2)
1...e6 2.Rd2 (The Rook self-interferes on the critical square d2 to avoid stalemate of the black)
2...Kf4 3.Rd4# (The mate is achieved with the check of the discovered critical piece).

It is clear that the problem has no other content, besides the theme we described as Indian appearing once.

Now we will see a problem, where the composer manages to show two Indian critical moves in each of the two variations.

 (Problem 128) R. C. O. Matthews, First Prize, “Die Schwalbe”, 1952 White plays and mates in 6 moves #6 (13+8) [ 8/6p1/1p1p4/1P3pP1/1P3K1p/2PRBP2/S2PpPB1/2Rsk3]

Try: {1.Rxd6? g6!}

Key: 1.Bh3! (The black is in a zugzwang situation).

If 1...g6
2.Bxb6 (critical piece the Bishop, over the critical d4) d5
3.Rd4 (the Rook self-interferes) Kxf2
4.Rxd5+ (the discovered critical piece gives check, new critical piece the Rook, over the critical d4) Ke1
5.Bd4 (the Bishop self-interferes) Kxd2
6.Bf2# (the discovered critical piece gives check-mate).

If 1...d5
2.Rxd5 (critical piece the Rook, over the critical d4) g6
3.Bd4 (the Bishop self-interferes) Kxd2
4.Bxb6+ (the discovered critical piece gives check, new critical piece the Bishop, over the critical d4) Ke1
5.Rd4 (the Rook self-interferes) Kxf2
6.Rd4xd1# (the discovered critical piece gives check-mate).

We observe how the composer enriched his problem with Indian intersections and how beautifully the roles of the two critical pieces in the two variations are inversed. Quite naturally, the problem was awarded with First Prize.

[This post in Greek language].