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Milko Bobotsov vs Fedor Bohatirchuk
Amsterdam Olympiad qual-2 (1954), Amsterdam NED, rd 2, Sep-05
Old Indian Defense: General (A53)  ·  1-0



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Jan-15-05  aw1988: 99...Ka7! draws.
Premium Chessgames Member
  beatgiant: <aw1988: 99...Ka7! draws.> Are you sure, and if so could you give the reason?

As far as I understand, the theoretical evaluation of these ♔♘♘ versus ♔♙ endings is completely determined by how far ahead the Black pawn is when it is blockaded. So it shouldn't change whether there's a mate or not, only how many moves it takes. Of course, that could be significant because of the 50-move rule.

I checked Nalimov tablebase, and it said 99...Ka7 leads to mate in 24 while 99...Kb7 allows mate in only 13. The last pawn move was on move 76, so move 124 would still be barely within the 50-move rule.

Jan-15-05  aw1988: Would you care to try and demonstrate a win for white?
Premium Chessgames Member
  beatgiant: <aw1988: Would you care to try and demonstrate a win for white?>

Excellent challenge, but 24 moves is a bit beyond my own human search horizon. I'm citing a result claimed in Nalimov tablebase.

I checked the Nalimov server at The claimed win begins with 99...Ka7 100. Kc7 Ka6 101. Kc6 and goes on for 22 more moves, with multiple branches.

Jan-15-05  aw1988: Ok, we can start from there. 99...Ka7 100. Kc7 Ka6 101. Kc6 Ka5.
Premium Chessgames Member
  beatgiant: <aw1988: Ok, we can start from there.>

It's pretty time-consuming and would generate 44 more posts as in <beatgiant: 102. Nbd5> <aw1988: 102...Ka4> <beatgiant: 103. Nbd5> etc., so I'm not going to demonstrate the win on the forum.

Instead, I'll give two pointers to check the source: explains the FEN notation used by the Nalimov server, and is the Nalimov server itself.

To use the Nalimov server, enter the FEN string for the position after 99...Ka7 100. Kc7 Ka6 101. Kc6 Ka5, which is 8/8/1NK5/k7/4p3/4N3/8/8/ w - - 0 0

The server outputs a list of each move with its outcome, with the strongest move first: Nb6-d5 M22, meaning White mates in 22.

You then continue the line with 102. Nbd5, make a reply for Black that you think is interesting, and enter the FEN string for the new position. Do that 22 more times, and you have the demonstration of the win.

Jan-16-05  aw1988: True enough. I'll test it out shortly. I don't know why I thought we could make a million posts on this page.
Jan-16-05  Pawsome: <As far as I understand, the theoretical evaluation of these versus endings is completely determined by how far ahead the Black pawn is when it is blockaded. So it shouldn't change whether there's a mate or not, only how many moves it takes.> The key to determining whether the ending can be won by the side with the Knights is something called the "Troitzky Line" named after the endgame study composer> It's described in the link below:
Hope this information is of some help.
Premium Chessgames Member
  Willem Wallekers: In 1977 Jan Hein Donner wrote an article on the research he did on this endgame. He drew two conclusions:
1. In the Troitzky line the pawns b6 en g6 really belong on b5 and g5. 2. When the pawn is on the line or behind it, it's a win for white in all cases, but if the the pawn is further advanced it's still a win in many cases.
Jan-17-05  Pawsome: Clicking on will take you to part one of "The Damned Pawn" a superb article by Karsten Muller that explores the mechanics of N vs. P endings. The second part of the article, which deals with the second "Troitzky line. The second article can be found in the Chess Cafe article. I Googled it by typing "Troitzky line into the search field.
Jun-29-05  Knight13: KNN vs KP endgame, huh. Rather rare. This would be a great game for endgame study!

Yet I don't understand 54... Ne7.

Jun-29-05  Resignation Trap: <Knight13> 64...Ne7 was played to eliminate White's last Pawn. In practice, this is Black's best chance!
Jun-29-05  Knight13: <Resignation Trap: <Knight13> 64...Ne7 was played to eliminate White's last Pawn. In practice, this is Black's best chance!> Thanks!

65. Nxe7 is forced or eles it would be draw.

Oct-30-06  gauer: Does anybody know whether there are any chessbase software extensions out there that make labels for corresponding squares or for sketching the Troitzky line boundaries, given a random positioning of the king(s) or other pieces in each of the smaller piece endings? For instance, chessbase has a "position search" function that allows piece maneuvers to be searched for at random, and I have also heard of Chess Query language. But I haven't found a way to try and see when it can report a winnable Q+PvQ ending or when a R+PvR ending is a draw, other than relying on a mere numerical eval. Is there a method to draw the maneuvering line which one should take as a method of attack, rather than simply rely on a computer eval of #38? For instance, when I purchased the 6-man ending tablebase, I thought that this strategical feature would be automatically implemented in.
Mar-18-07  Mendrys: After ....Ka7 107. Kc7 Ka8 108. Nd5 Ka7 109. Nb6 we have:

click for larger view

this would be stalemate of course if there were no pawn but black is forced to move his pawn twice more while white sets up the mate 109....e3 110. Nc8 Ka8 111. Nd7 e2 112. Ndb6#

Mar-18-07  aazqua: 45 h5?? Why? Why give the bad bishop new life and create a passed pawnwhere one could not have existed?
Jul-25-08  4tmac: Blacks 99 was not best and his 88 was even worse but overall both players did pretty well especially white from move 100 on. Many of these moves were counterintuitive but white played near perfect at the end.
Premium Chessgames Member
  Check It Out: incredible
this endgame is beyond me
Sep-07-13  Xeroxx: good technique
Premium Chessgames Member
  GrahamClayton: Exemplary technique by Bobotsov, as he would have mated with just three moves left before the 50-move rule came into effect. I am right is assuming that the 50-move rule was in effect in 1954, or had FIDE made an exception for this ending?
Sep-30-15  The Kings Domain: Did black resign out of weariness? :-) This puts the O in "Overplay".
Jun-23-16  Smothered Mate: Assuming the standard 50 move rule applies, and using ​ : ​

65. ... Kxh4 ​ draws

88. ... Kb6 ​ loses; Kc5 was best and Kb7 was the only other drawing move.

89. Kd7 ​ and ​ 90. Kc7 ​ (both played) were both only-winning-moves.

92. Nd4 ​ was inaccurate but still wins; Nc3 and Nf4 were the optimal moves.

Due to that inaccuracy, ​ 93. Ne6 ​ and ​ 95. Ncd5 ​ (both played) were both only-winning-moves.

96. Ke7 ​ and ​ 98. Kd7 ​ (both played) were both only-winning-move, and by large margins.

106. Kd7 ​ was also an only-winning-move, although Kd6 and Ne6 were _not very far_ from also winning.

Jun-18-18  Omnipotent00001: 62...Kh5 or Nc6 lose in 67 moves.
Dec-21-18  m.okun: As long as there is at least one pawn on the board, there is no theoretical draw with two knights. What Bobotsov brilliantly proved.
Oct-01-22  Muttley101: <m.okun: As long as there is at least one pawn on the board, there is no theoretical draw with two knights. What Bobotsov brilliantly proved.>

This is incorrect, because (as mentioned above) the win of 2N vs P depends on the P's location, as the player with the pawn always has the possibility of advancing it to queen when it is no longer blockaded. The point is, the pawn can be used a diversion because if the player with the 2N isn't mating it must be captured, and the resulting ending of 2N vs K is drawn.

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