What are the hardest pawnless endgames that go over the 50-move rule?

Question

I know two pawnless endgames that go over the 50-move rule.

King and 2 Bishops vs. King and Knight = 70 moves average.

King, Rook and Bishop vs. King and 2 Knights = 200 move average.

What others are there?

I feel the FIDE should reform the 50 move law & apply exceptions to these cases (would be epic a championship game decided in one of those endings!) — Fernando Gonzalez Sanchez, Jan 12 '15 at 00:21
@FernandoGonzalezSanchez They did, for a while. It made very little difference, since these endgames come up very rarely in real life. So they moved back to a uniform 50 moves. — David Richerby, Jan 12 '15 at 22:04
Good to know, btw a similar question: http://chess.stackexchange.com/questions/351/what-is-the-status-for-seven-man-end-game-table-bases — Fernando Gonzalez Sanchez, Jan 19 '15 at 02:40

score 9 · Answer 1 · edited Apr 29 '20 at 18:22

9

If you mean "hardest" == "longest": There are 7-man table bases available and it is said that the longest pawnless ending takes 549 moves. It is KQB vs. KRBN.

Resources: http://tb7.chessok.com/articles/Top8DTM_eng

And in case you are too lazy to go through the moves by yourself :-): http://tb7.chessok.com/probe/745/61

I think that is what is known today. I would not be surprised if even longer pawnless endings exists with 8 pieces on the board.

edited Apr 29 '20 at 18:22

Rewan Demontay

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answered Jan 13 '15 at 20:45

Jagu

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Do you know what the winning chances are in this endgame if it was a random position? – user5649 Jan 15 '15 at 14:38
No, I don't have any other information on the winning chances for this endgame. – Jagu Jan 16 '15 at 19:35
ah, cuz that's what i kinda wanted to know, it had to be at least 90% winning chance – user5649 Jan 17 '15 at 14:54

score 3 · Accepted Answer · edited Aug 09 '17 at 05:08

According to wikipedia http://en.wikipedia.org/wiki/Pawnless_chess_endgame, section "Endgames requiring more than 100 moves to win", the longest is

R+N vs N+N = 243 moves with 78% of winning chances.

R+B vs N+N = 223 moves with 96% of winning chances.

R+N vs B+N = 190 moves with 72% winning chances.

and the list goes on...

Another way is looking at the database of mutual zugzwangs at http://chess.jaet.org/cgi-bin/mzugs?sort=wmaxdtm sorted by maxdtm (depth to conversion or mate).

John Nunn's book "Secrets of pawnless endgames" (I love that book) in the 2nd editions expands coverage to some of the endings mentioned (although very briefly).

What are the hardest pawnless endgames that go over the 50-move rule?

2 Answers2