Friday, May 23, 2008

Selfmates (1)

Today's post is the first containing selfmate problems. The selfmates (also the helpmates, the fairies, etc) are heterodox problems. The selfmates differ from the orthodox direct-mates on the goal.

Selfmate is a chess problem where White, who plays first, must force Black to give mate in a specified number of moves, while Black tries to avoid this.

(Problem 90)
Wolfgang Pauly,
Selfmate in 2 moves (= White plays and forces black to give mate in 2 moves).
s#2 (10+4)

The problem-90 is a relatively simple example of a selfmate problem. It was composed by Wolfgang Pauly, was published in the book "The Theory of Pawn Promotion" in 1912, and is a selfmate two-mover : White plays first and forces Black to give mate in (at most) 2 moves.
In two moves only the black Bishop can give mate. If White leaves no other choice to Black than Bxg2#, then the problem is solved.
White could :
(1) move the Bishop, but it is not good because it allows Black to play his bishop without capture, delaying the mate after the second move,
(2) move the Knight, but this gives flight to the black King,
(3) make promotions 1.g8=Q or 1.g8=R, which is not good because, after 1...Bxg2+, the promoted piece can defend with 2...Qxg2 or 2...Rxg2,
(4) make promotion 1.g8=S+, which checkmates Black, totally wrong for a selfmate,
(5) promote 1.g8=B, which is also not good, since after the moves [1...gxf6 2.exf6 Bxg2] the white Bishop can interfere with 3.Bd5,
(6) try 1.e6? exf6! (and 2...f5)
(7) try 1.fxe7? Kxg7! (similar defend after 1.f7).

The white move, which forces Black to mate in 2 moves, is :
Key: 1.c8=S!
(promotion only to Knight, because any other piece could interfere in diagonal h1-a8 after the move Bxg2. There are two variations, the simple...)
1...exf6 2.exf6 Bxg2#
(...and the cunning...)
1...e6 2.g8=B Bxg2#
(...which is effective only because the path of the wB towards d5 is blocked by the black move 1...e6).

Other kinds of selfmates

There is the type reflexmate, in which white forces black to give checkmate, under the additional condition that, if either side can checkmate, then it must checkmate on the move. When this condition is valid only for black, then the problem is semi-reflexmate.

There is the type black maximummer, in which black must always make the longest (geometrically) move available. The length is measured from the center of the departure square to the center of the destination square.
Usually this condition is used in selfmates.
With the term maximummer we specify the problem where white and black must play the geometrically longest move.

There is the type series-selfmate, (one kind of the Series chess problems), where white alone plays a number of moves without response from the black, and in the end black makes a move and checkmates.

In the next selfmate-91, by Rudenko, we see the themes of X-flights and of multiple pawn promotions (Allumwandlung).

(Problem 91)
V. Rudenko,
First Prize, “F.I.D.E. Tourney”, 1962-3
White plays and forces black to mate in 3 moves
s#3 (9+9)

There are some tries: {1.f8=Q+? / f8=S+? Kd5-e4!}, {1.f8=R+? Kxc6!}, {1.Rb3? Ke4!}, {1.Rb4? Ke4!}.
Key: 1.Rb2! (zugzwang)
1...Kc4 2.f8=Q+ d5 3.Qa3 h2#
1...Kc6 2.f8=S d5 3.Sf7 h2#
1...Κe6 2.f8=Β+ Κf6 3.Βd5 h2#
1...Ke4 2.f8=R Ke3 3.Bd5 h2#
or 2...d5 3.Rf3 h2#

A page for selfmates, at the site of the B.C.P.S., may be found here.

(This post in Greek language).

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