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

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!) Commented Jan 12, 2015 at 0:21
• @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. Commented Jan 12, 2015 at 22:04
• Good to know, btw a similar question: chess.stackexchange.com/questions/351/… Commented Jan 19, 2015 at 2:40
• @FernandoGonzalezSanchez not the same :l Commented Jan 20, 2015 at 16:42

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).

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.

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.

• Do you know what the winning chances are in this endgame if it was a random position? Commented Jan 15, 2015 at 14:38
• No, I don't have any other information on the winning chances for this endgame.
– Jagu
Commented Jan 16, 2015 at 19:35
• ah, cuz that's what i kinda wanted to know, it had to be at least 90% winning chance Commented Jan 17, 2015 at 14:54