I spent almost an hour trying to solve this one:

http://www.chess.com/forum/view/more-puzzles/mate-in-two34

It's "just" a tempo problem btw (a very good tempo problem, don't misinterpret), after all possible black moves there is mate - except for one (unpinning the rook). Just find that mate too and you're set

Ah, I missed that one when someone posted it last year. But yes, I soon saw that it was almost a zugzwang position, and I eventually found the right move after trying all kinds of waiting moves first. Still, a good exercise.

I found the solution after many tries, but anyway I'm very surprised that there is a mate in two that chess engines can't solve... (if I run the analysis I get Bxe4 which is mate in three)

no good..

Which engine(s) did you use?

Hunt around, find that you don't have a response to e5 because Bb6+ can be taken by the no-longer pinned rook, and then it becomes easy.

Nice problem though :)

When I wrote that, I was using Robbolito which is not able to found the mate in two... but I just downloaded the latest Fire, and this one instead has found the solution

Qg5 was a mate in 3 because black has Ra6+, neat solution that I didn't find.

This was posted 3 yrs ago, so I don't know if anyone is still tracking this puzzle. When I searched for most difficult mate in 2 puzzle, this was the first result. I made a couple of mistake before I got the solution, but after solving this puzzle I analyzed the board further and found out this puzzle may be wrong. After Bc6 if black replies with Bf3 I couldn't find the move that would mate the Black king in the next move.

Once you solve the puzzle or request for the solution, you'll find that the list of alternate moves appears in the moves list. For 1... Bf3, the reply is 2. Qg1#.

Interesting indeed! So it's basically a Zugzwang problem...

I did not find the correct solution. However in pratice, the game is easily won for White (I found a mate in 4 for example) of course.

As to engines, well... Stockfish 5 on my Android phone (Droidfish app) found it immediately.

thanks for the problem.  im not the biggest classical chess problem solver but i felt like looking at a couple tonight and when i googled the most difficult mate in 2 chess problem i got this one.  im not certain its the most difficult.  frankly it seemed pretty typical for this genre of problem.  it turned out to be the first move i looked at.  once you begin by choosing the most obscure or un-natural looking move which doesnt lose immediately and analysing possible replies and retorts they seem to either mostly workout in which case you switch one bizzare looking selection for another which addressing the shortcomings of the first or you stumble upon the correct solution outright.  i havent seen anyone else post tge solution.  spoiler alert if youre looking for tge answer its the simple waiting move ...Qh8 all replies lead to one mate or another on the next move.  Regards,   The Alcoholic

Zugzwang kills :D

Not very difficult if you see that black is very close to zugzwang. And then it's time for a conundrum why some bishop moves are not good. When you see e5 then everything is clear.

why do you even move the bishop?

just move the pawn...check and mate?

No, Kxd3.

revist 07.06.15 Difficult indeed, diabolical setup...

I was looking at the problem again today, and I thought what would be Black's defence against 1 Qxe7 ? 

Edit: OK, he can give some annoyance checks then, starting with the rook.

Thanks for a great puzzle.