Are there any hard mate-in-2 problems?

Question

I'm interested to know if there are any particularly challenging mate-in-2 problems. Since the second move will be essentially forced, the problem essentially comes down to 1 move. Typically, the search space is not enormous: white (assuming white to mate) does not have many pieces for the first move, and black has even fewer.

So: are there any good examples of hard mate-in-2 problems? And what are the elements of such a problem?

Answer 1

As you say, what could be difficult about a mate-in-2? Or, how can make mates in 2 difficult? The answer is probably one of the most common problem devices, the Grimshaw, named after 19th century composer, Walter Grimshaw.

The basic idea is that two opposition pieces are each stopping a mate so you make a move which has to be met by one or other of the pieces moving to a square where it blocks the other piece. These subtle first moves can be very difficult to find, although the level of difficulty is in the eye of the beholder. Three times world puzzle solving champion, GM John Nunn, almost certainly doesn't find the same problems difficult that I do.

Here is a simple "Grimshaw" mate-in-2:

[Title "White to play and mate in 2"]
[fen "8/B2K3Q/5p2/3k4/2p2P2/p6p/r7/b7 w - - 0 1"]

Knowing it's a "Grimshaw" and seeing as how black only has 2 pieces that can interfere with each other makes it much easier, but without that knowledge it would be frustrating tough.

Of course, top problem solvers know all about Grimshaw which makes 2 movers easy for them.

Answer 2

Hard for whom indeed.

• Even the chess computer from the museum can solve a #2 in a jiffy.
• Take a GM with no experience in solving. I daresay: no particular advantage over a ELO 1800 unexperienced solver.
• On the other hand, if you are a composer yourself and know all the tricks of the trade, hardly a #2 will stump you. For solving contests, this might be turned against you (I ran into a problem where the solution was hacking away a piece, nobody of the illustre circle solved it.)

The answer to your second question (what makes up difficulty) thus strongly depends on the solver.

• In general, the more tactical chaos, the more difficult the problem.
• Long moves.
• Pin defences.

I googled "difficult twomover", the result was essentially nil. :-)