Christmas puzzle: What were the previous moves?

by Frederic Friedel
12/26/2019 – Christmas Puzzle week, which we bring you for the twentieth year in succession, is time for unusual and entertaining puzzles — tasks that are not amenable to computer assistance, but require human ingenuity. Try, for instance, to imagine how the position in the picture could have possibly arisen. Determining that needs lateral thinking. One of the foremost composers of chess problems "out of the box" sent us some highly entertaining examples. At least one of them looks quite impossible. Merry Boxing Day!

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"Out of the box"

During the Christmas puzzle week, which we bring you for the twentieth year in succession, you need to be prepared for puzzles that cannot be easily solved with a computer (the point of this endeavour). We give you tasks which require you to think all by yourself. But unlike in the past we will not be giving you a separate instalment every single day between Christmas and New Year. Just occasional entertainment during the holiday season.

Today we bring you a special puzzle by Werner Keym, who is one of the most creative problemists I know. He specializes in problems involving castling, en passant captures and pawn promotion. For many years I have enjoyed his problems, which I often encountered. Many have the advantage of not being prone to instant solution by chess engines. They force you to think. His most recent English language book, "Chess Problems out of the box," is going to keep me busy for a long time to come. It is one of the most entertaining works I have ever encountered (and it is competing with Loyd, Dawson, Fabel, Smullyan and co.). You can get yourself a copy here (€12/US $12 + postage €2/€4).

And now without further ado here is a Christmas puzzle Werner Keym sent me:


It looks impossible: Black can always escape White's attacks, at least for three moves, e.g. 1.♗xf5+ ♚xc7 2.♖g7+ ♝f7+ 3.♖xf7+ ♚b8 6.♖b7+; or 1.♖g7 ♚xc8 2.♗xf5+ ♝d7 3.♔d6 ♝xf5 4.♖g8#.

The only way to mate in three seems to be after capturing en passant on f6. But in chess problems that is only allowed if you can conclusively prove that Black's last move can only have been a double-step of the pawn: f7-f5. You must show that it was the only possible move, i.e. that any other Black move previous to the position above was not possible.

Let us make it absolutely clear: you need to find a position in which Black and White played one legal move each, and then in the diagram position Black played f7-f5, allowing White to play 1.e5xf6 e.p. and deliver mate on his third move. Can you find the previous two moves?

If you are getting a feel for this kind of problem, here are a few more. The following two are real classics — you see them everywhere. They are also fairly easy. The first is by Dr Niels Høeg from 1916, the second by Raymond Smullyan in 1980. In each case the question is what could have been the previous move or moves, how could these positions have occurred?

How did this happen — what were the last moves?

The next two are harder but very pleasing to solve:

How did this happen — what were the last moves?

In the first diagram (by Werner Keym, Die Schwalbe 1979) Black is in check. What were the previous moves? In the second diagram (by Niels Høeg, Skakbladet 1924) the question is how could that position have arisen? You must find a legal position that can lead to the above diagram in three moves.

The solution to these problems will be given in the third week of January.


Editor-in-Chief emeritus of the ChessBase News page. Studied Philosophy and Linguistics at the University of Hamburg and Oxford, graduating with a thesis on speech act theory and moral language. He started a university career but switched to science journalism, producing documentaries for German TV. In 1986 he co-founded ChessBase.
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the druge the druge 1/10/2020 09:23
Are we likely to see the solutions any time soon? ("later this week")
antroplaza antroplaza 1/4/2020 01:33
Thank you Chess base magazine for everything You do! Lazar Crkvenjakov.
Frits Fritschy Frits Fritschy 12/27/2019 08:47
As I still don't understand what we might be disagreeing about, I propose to disagree that we disagree, or better still: that we agree on somehow agreeing.
Thanks for the link, maybe the following will interest you too: (I hope this will be accepted by the human or electronic moderator).
Mikhail Golubev Mikhail Golubev 12/27/2019 08:09
2 Just Passing By:

Sorry but I think that my solution is correct, and it's not relevant that instead of ...f7-f5 (which led to the position in question) Black technically also had an opportunity to play ...Kd7xc7.

...f7-f5 was "the only possible move" that led to the position in question - but this does not mean that it was "the only possible move" in the position when Black made this move!)
chessbibliophile chessbibliophile 12/27/2019 06:08
Frits Fritschy,
Let us agree to disagree on the Merlin analogy. That’s beside the point. More pertinently Keym’s reasoning was the same as yours. The Black king could not have got into this position with White moving first. So it had to be Black moving first. As for the position, it’s right here:

Incidentally, the original German edition, “Eigenartige Schachprobleme” (Curious Chess Problems) is made available for free by the publishers. Readers can download it from the net and it is perfectly legal.
Frits Fritschy Frits Fritschy 12/27/2019 05:27
Don't understand what you mean with the 'oversight'. The magician Merlin lived backwards in time, ever getting younger, maybe that wasn't clear to you? Seemed a fitting image here.
As I understood the problem, there is no mate in two with white to move, as then the position isn't possible by lack of any legal previous move by black. So black has to move first and then white can always mate in two, both after Kxe6 and Kxc4.
Still I would like to know how you got the diagram in your first comment. Only possible for premium members?
chessbibliophile chessbibliophile 12/27/2019 05:03
Frits Fritschy,
Sorry, that was an oversight on my part. The position with the author appears next to the cover of the book shown in the article here (not on the cover itself). It has a curious background. Werner Keym had composed it in 1968 and it was published again in 2002 on the occasion of his 60th birthday. According to him this time it was set as a “task”. Most readers assumed, White moved first and found the mate in two moves. However, they were also expected to find a mate in two with Black moving first. Now that amounts to a helpmate. Interested readers can still find it all in the original German version of the book, “Eigenartige Schachprobleme” (Nightrider Unlimited, 2010).
Frits Fritschy Frits Fritschy 12/27/2019 12:55
Even after the modification in the text, there are two solutions to the Hoeg problem. It is essential to state that black's last move was Bc1-b2 (by the way: not Bc1xb2).
Frits Fritschy Frits Fritschy 12/27/2019 12:48
Didn't take much time to see the, let's say: 'Merlin trick', but it still took me some time to find the solution. But: how did you get in the diagram?
Frits Fritschy Frits Fritschy 12/27/2019 11:56
Just passing by:
f7-f5 is the only LAST possible move by black, which makes exf6 e.p.+ a possible solution. Black's last move couldn't have been with king or bishop. Moving backwards in time isn't easy, as Merlin from the king Arthur saga can affirm...
Just Passing By Just Passing By 12/27/2019 10:55
Mikhail, it has to be the only possible move for black. The line you give would be good, except for the fact that Kxc7 is possible. As a matter of fact, Kxc7 is possible always, since with the black pawn on f7 and black to move, the c7 pawn is undefended...

I have spent entirely too much time of my holiday thinking about this and decided that it has to be a touch move for black, else there is no possible way for the black to have f5 as only possible move, as Kxc7 is available.

I know this is not the right answer though, but I wanna enjoy my holiday!!!
Mikhail Golubev Mikhail Golubev 12/27/2019 10:08
Re6 takes something on g6, check, and Black plays ...f7–f5
chessbibliophile chessbibliophile 12/27/2019 04:45
The cover of Werner Keym’s book shown here also shows a two-move problem.

The solution is simple and elegant. Your move!
Frits Fritschy Frits Fritschy 12/26/2019 02:33
I think I found the problem I meant: N. Petrovic, Problem, 1954, 1st/2nd Prize 4th Thematic Tourney (fen):6K/7B/4Pk/6Q/4Q/8/B (Last six single moves?). Well, my attempt is a single move longer (and without promoted queen), but there is still something nagging that I've seen my idea before. Can anybody help me out?
Frits Fritschy Frits Fritschy 12/26/2019 02:01
A bit of a puzzling way to present these puzzles. 'What were the last moves?' The second one: well, Kd8-c8 surely isn't the intended solution. 'Clearly the final move was ...♝c1-b2#' That's not so clear: what about 1 b2-b3+ Ka4-a3 2 Ba2-b1 Bf8-g7+ 3 Nd3-b2 Bg7xb2#? So the right stipulation should be: 'Black has just played Bc1-b2#. Which were the last two white moves?' That really has just one solution.
By the way, the first problem can be easily extended. See this position (fen notation): 3N/3K2p/4Pk1N/8/5P1P/8/8/BB4R. Which were the last four white moves? I might try to get a more efficient setup, but I have a vague memory that it was already done.
algorithmy algorithmy 12/26/2019 11:07
As many readers here, I thought I found the solution when I saw that White can take the pawn on f5 en passant and then the solution would be: K × c7 2. Bf4+ Kd8 3. Nb7 #. But then I noticed that it's very difficult to envisage a position where the last move of black would be advancing the pawn from f7 to f5, but then I saw that it could happen as follows: black has just moved a piece , let's say a knight, to g6, and then white captures in g6 by his rook delivering a discovered check at the same time, and then black advances the pawn to f5 to cover the check, and here we reach the position where white can take the pawn on f5 en passant.
Very nice puzzle! The most pleasing part about these puzzles is, of course, the riddance of computer, but it’s the kind of positions you will never face in a real game!

Happy Christmas, every one
Muhammad from Egypt