Interesting triangulation

[h.g.muller]

In the Makruk end-game King + Silver General (S) + Ferz (M) vs King I encuntered the following manoeuvre to triangulate. It seems of general interest, as this is a case where really everything seems to be most unfavorable: neither Silver nor Ferz can triangulate, and the Silver breaks diagonal symmetry, so rank and file edge are not equivalent. So that the usual trick of diagonal flipping does not help; there only is a mate along the edge file.

8/8/8/8/1QB5/8/k1K5/8 w

B represents Silver, Q represents Ferz

With black to move this would be a simple mate in 3: 1... Ka1 2. Mc3 Ka2 3. Sb3+ Ka3 4. Mb2#. But with white to move you have to shed a tempo, and this delays the mate by 15 moves, reaching the same board position with black to move after white's 15th move.

Code: Select all

[Event "?"]
[Site "?"]
[Date "?"]
[Round "-"]
[White "?"]
[Black "?"]
[Result "1-0"]
[Variant "makruk"]
[FEN "8/8/8/8/1MS5/8/k1K5/8 w 0 1"]
[SetUp "1"]

{--------------
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. M S . . . . .
. . . . . . . .
k . K . . . . .
. . . . . . . .
white to play
--------------}
1. Sd3 Ka1 2. Se2 Ka2 3. Sd1 Ka1 4. Sd2 Ka2 5. Sc1 Ka1 6. Kd3 Kb1 7. Kd2
Ka2 8. Kc3 Kb1 9. Sd2 Ka1 10. Kb3 Kb1 11. Mc3 Ka1 12. Kc2 Ka2 13. Mb4 Ka1
14. Sc3 Ka2 15. Sc4 Ka1 16. Mc3 Ka2 17. Sb3 Ka1 18. Mb2
{White mates} 1-0

The critical position is this:
8/8/8/8/1Q6/2K5/3B4/1k6 b - - 0 1


This is the last position where black has move choice, and after he chooses, the trap snaps shut by eaither playing the white King directly to c2, or doing it via b3 (which requires an extra back-and-forth move of the upper confining piece to make it possible to appear reach c2 unobstructed by the blackKing.) It seems that you can do this with any pair of pieces capable of back-and-forth motion and are not both color bound.

[Edit] Diagrams do not work on this forum?