What are the rules for this mate now (lone K vs K,B,N)? If the superior side does not know the technique, what does the TD do? Does the 50 move rule still apply? Does the TD adjudicate? Thanks!
The inferior side should keep a complete score, so that he can claim a 50-move draw at the appropriate time.
If scorekeeping is not required (because the game is quick-rated or blitz-rated, or the inferior side is under 5 minutes), then the inferior side could ask the TD to watch the game, keep track of the move count mentally, and declare a draw at move 50.
There are pitfalls, though. First, the TD may decline your request to watch the game because he’s too busy. Second, the TD’s move count would probably start at 1, even if there have already been 10 or 20 moves played since the last capture. Third, the TD may become distracted with other problems in the playing hall, and have to abandon the move count. Fourth, etc etc etc.
Also, you cannot use the clock’s move counter, by itself, as evidence that 50 moves have been played. Move counters sometimes become inaccurate (there is an illegal move that causes an extra clock press, or somebody forgets to press his clock, etc). Nevertheless, the move counter might help the TD in his mental move count. If, for example, when the request is made he notices that the move counter reads 46, he can make a mental note that he can stop the game at move 96, and if there is an extra clock press or something along the way, he can then change his mental note from 96 to 97.
But all this is highly speculative, and TDs may differ in their approaches, so lotsa luck.
Bill Smythe
Any adjudication depends on best play by both sides, and best play is a mate in 38 at worst. The players can use the 50-move rule and the TD can use the 75-move rule if the players are clueless.
If the TD is counting he can use the partial scoresheets to verify a minimum number to start at (15F4a) but if both players agree on a number the TD can use that without having to try to determine a number.
If the side with the bishop and knight wants to end it by claiming a draw but the other side wants to fight it out then a draw can be awarded (the superior side does not want to continue so penalize the player all of the time remaining and then the ruling on whether or not the opponent has enough material to win the game on time is an emphatic NO with the result that the game is drawn). I have seen lone king players continuing to play in the hope that they get a win if the opponent flags.
I was working one tournament where there was a bishop+knight mate, and the player missed a move while driving the king along the edge, but figured it out in time to mate on about move 48.
Back in the 70’s the ‘other Larry Evans’ used to offer to play that ending at the Chicago Chess Club for 25 cents, you had unlimited time, he had one minute on a BHB clock. I never saw him lose the quarter.
On the other hand I remember a tournament where a young player had a rook+king vs king ending and couldn’t figure out the way to mate his opponent in 50 moves. (I showed him the technique afterwards, but it went in the books as a draw.)
Don’t get me started. We had a scholastic game once where a young woman had Queen, Rook, and King vs. lone King, had no clue how to mate her opponent, and was low on time. The catch was that there was also a pair of opposed pawns (one of each color). Had she flagged, she would have lost, since her opponent still had that pawn (however unlikely its chances of ever promoting). I breathed a sigh of relief when she stumbled on mate by blind luck after an interminable series of random checks with the Queen and/or Rook.
If it’s check, it can’t be stalemate, so giving random checks when you’re up a queen and rook isn’t all that bad a strategy.
Bill Smythe
Rule of thumb in beginner scholastics:
K+Q vs K is a draw 50% of the time.
K+2Q vs K is a draw 90% of the time.
There are no longer any exceptions to the 50 move rule. The tablebase analysis has discovered quite a few previously unknown positions where it takes more than 50 moves with best play to mate (or make a capture or make/force a pawn move) so it was impossible to maintain a list of exempt positions.
In general, no, but when you’re about to flag, and the opponent has potential mating material, it can be disastrous. It’s also incredibly frustrating to watch, knowing that there’s a simple and basically automatic mating procedure.
Before I get too high and mighty, though, I must admit that in my one and only rated blitz tournament (in 2013, by which time I had been playing tournament chess for about 28 years), I had Q & K vs. K and managed to stalemate my opponent. That’s an automatic procedure, too, and one that I know. But it’s funny how the brain works (or doesn’t) in time pressure.
Actually, this is only true OTB. In correspondence chess, ICCF disallows the 50 move rule in seven man tablebase positions.
Alex Relyea
I guess if you’re playing computer assisted correspondence, you can just adjudicate once you’re into a tablebase position.
Yes. Of course in some positions the result of the adjudication has changed fairly recently.
Alex Relyea