Author: Ricardo Gibert
Date: 09:54:30 11/11/99
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On November 11, 1999 at 03:09:38, Bernhard Bauer wrote: >On November 10, 1999 at 11:36:09, Ricardo Gibert wrote: > >>On November 09, 1999 at 22:04:30, Bruce Moreland wrote: >> >>>On November 09, 1999 at 18:42:24, Andrew Dados wrote: >>> >>>>Hello, Scott! >>>> Bad news here: 2 Knignts can not mate lone King... You may have found some >>>>positions where 2 N mate King+Pawn; not sure what is longest mate there, but >>>>there are (KNN vs KP) positions where definetely more then 50 moves without >>>>progress (moving a pawn or capture) is needed. As I remember fide adjusted 50 >>>>move rule for this case (and some others) and allows now 150 moves with no >>>>progress for KNN vs KP (correct me if I am wrong here). >>>> >>>>-Andrew- >>> >>>Black king h8, white king h6, white knight f6, white knight h4. White to move >>>mates in one with Ng6#. >>> >>>It is not a forced mate, because black's previous move must have been Kg8-h8. >>>He simply could have played Kg8-f8 or Kg8-f7 and avoided the mate. >>> >>>bruce >> >>A final position where 2 Ns mate a king _can_ be forced (by transposing KNNK via >>a series of exchanges). I have a recollection of an endgame study by Troitzky >>that ends this way. There also endgame studies where the final position has K+B >>mating K+B, etc. There is a possible bug with many programs that declare such >>endings as draws when a mate in one may still be possible. I believe that Fritz4 >>is one program that behaves erratically when cofronted by such examples. There >>are no mate in twos with just KNNK that can be forced of course. > >Would you be so kind and post those positions? >I would appreciate to have a look at them. >Kind regards >Bernhard It is very difficult to search for these in my books on endgame studies (you have to run through practically all of the solutions and when you consider that underpromotion is a frequent theme, there is no simple way to narrow the search), so I took a shortcut and composed my own. I did not want to waste too much time on them, so of course these are pitiful compositions and are only intended as a demonstration that studies are possible based on such mates. The following one is a white to move and mate in 3: k2n4/8/K2b1Q2/8/2B5/3q4/8/8 w - - 0 0 1 Qxd8 Bb8 2 Qd5 Qxd5 3 Bxd5 is mate with opposite color Bs. The next one is a white to move and mate in 4. Unfortunately, there are many alternate solutions that do not include a mate with 2 Ns. I lost patience with it and my attempt to fix it with a pawn on c7 did not do the job. I'm a hopeless composer, but at least there are no quicker solutions. 1k2NN2/8/K3N3/8/8/8/8/8 w - - 0 0 1 N8c7 Kc8 2 Na8 Kb8 3 Nfd7 Kc8 4 Nab6 is mate with 3 Ns, while 3...Kxa8 4 Nc7 is mate with 2 Ns. White can vary on moves 1 & 2 and still mate in 4 without having to mate with just 2 Ns. To fix this probably requires adding more material to the board that gets exchanged off. Not easy. Oh well. The book I remember that had the mate with 2 Ns was one by Troitzky. I can't find the book. It must be in a box in the attic, but I don't feel like retrieving it.
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