I enjoyed this chess problem

https://www.youtube.com/watch?v=bsxDI0pKlug

Pretty amazing.

That is a good one, not seen it before. While the initial move is obvious (for intermediate players, like me, and up) I must admit I didn’t spend the time to work out the importance of the choice of next move, though I did spot the likely need for

an underpromotion to knight, as that is the only piece that will be able to give mate. I also didn’t calculate the consequences of Ng6 as opposed to Nf7.

I do recall seeing in a chess book a problem by the same composer (Otto Blathy) which was white to play and mate in 104 moves! Naturally it didn’t have the subtlety of this one, but was based on a similar idea of Black only being able to shuffle pieces to and fro.

I wonder if anyone has a proof game for these being legal positions? That is a normal requirement for serious chess problems/studies, though I believe subcategories exist for non-legal positions.

It’s a nice problem, though I’m pretty sure the distinction in Dead Cat’s spoiler doesn’t really matter.

The main trick here is getting the tempo right. That took a good little bit of calculation. Reasonably straightforward calculation, but important to get right otherwise you end up in a drawn position.Reminds me a bit of the thread on that chess problem that was supposedly impossible for a computer to solve a few months back, but pretty dead easy to force a draw for white in a situation where black has overwhelming material advantage. This one is more nuanced and has two tricky bits, though.

Here’s what I was thinking of.

ETA: Spoiler tagging just in case.

This terrible chess player would have nixed black’s knight, like the solution offered, then promoted the pawn to a Queen and hoped for the best. I can’t see 16 moves ahead. Hell, I can’t see three moves ahead. Reason #468 while I’ll never be a great chess player.

Thing is, here most of the moves are forced for black if you glom on to what you need to do relatively quickly. The way I saw it is that taking the knight immediately forces black to only having one available move, shuttling the queen back and forth. So the next thing to consider is how to mate. The black knight is protecting the black rook by the white king, so that obvious mating move is probably not going to be the solution of promoting to queen and taking out that rook. Next is to remember, this is a chess puzzle, and underpromotion seems to show up in these things occasionally. Getting a knight to C3 while white’s queen is on A1 is a checkmate. We can reasonably be sure that’s going to be the solution. Now comes the tricky part. Figuring out how to eke out the correct number of moves so you can get to C3 while black’s queen is on A1. I admit, I did this over the board, though, not in my head.

One simplification in the analysis, and which is also incidentally why the single-step pawn move is the only way to reach the solution, is that every knight move must change colors, and so must every queen move. And since the knight must move to the color the queen is not on to win, it (and its ancestral pawn) must always move to the color the queen is not on.

The choice of first move to make after the promotion is not critical; a mistake there can be corrected, and so it just means that the checkmate takes a little longer. But the choice to move ahead one space instead of two is critical, because that’s the only move where white can choose which color to move to.

Except that the “wrong” first knight move doesn’t take longer. In the given solution, the knight goes f7 - d8 - e6; it works the same to go g6 - f8 - e6. In the wrong line he gives in the video, the problem isn’t the first knight move, it’s that the knight takes the c4 pawn before the c5 pawn. Taking c4 first allows black to later play the c5 pawn to c4, which breaks the color correspondence between the knight and queen.

I find that the key in a problem like this is to visualize the mate, and work back from that. In that case, you find yourself realizing the tempo issue eventually.

borschevsky is right, btw. Didn’t understand how he got all involved in something else moving besides the queen.

Thanks guys - my post was based on an uncritical viewing of the video, I did think at the time that white might be able to win based on either knight move but didn’t bother to check. I assume the composer was well aware of that. As an entry into a study competition, I suppose this composition might lose some credit for the dual solution, but in my view, the idea of move 2 needing to be h3 instead of h4 makes up for it.

A lock-up based puzzle like this is going to have a nigh-infinite number of solutions, because you can always take your time wasting moves before going in for the kill.

Not really because of the 50 move rule.

Sure, it’s finite, but do you have any idea just how many move-wasting sequences you could have in the span of 50 moves?

I saw this in Chess To Enjoy. I remember that book very well because it actually had, well, fun stuff instead of going on and on and on about controlling the center and establishing pawn structure and setting up combinations and all that other eternally tedious stuff that generally puts me into a catatonic trance by about the third paragraph.

Anyway, the theme of this is “one pawn destroying the entire enemy army”. I read the solution, and it’s pretty elementary, and to be honest, I think y’all are overanalyzing it just a tad. Here’s how it goes:

  1. The first thing to do is capture the knight with the king. Or, to put it in extraordinarily technical terms, “Kxe1”. This immediately puts Black in a position where it can only shuffle the queen between the two open spaces (a1 and a2, if I’m not mistaken, and I’m not), provided that you don’t do anything incredibly stupid like move the king, and for purposes of this problem I’m going to just assume that because I don’t have all week for this.

  2. Now you can deliver checkmate by taking the rook on b3 with a knight. However, you have to do this while the enemy queen is at a1, the reason for which I certainly hope is obvious. As knights always alternate between white and black spaces, this effectively means that the knight must attack a white space at the same time the queen is on a black space, and consequently, it must always enter the color opposite where the queen is before its move.

  3. As the pawn to be promoted will also alternate between white and black spaces after its first move, and will move every turn after the first (because, y’know, that incredibly stupid thing I mentioned earlier), it must also always enter the color opposite where the queen is before it moves. So your second move must be h3.

  4. Lastly! Before taking the rook, it’s necessary to take the pawns on c5 and c4, in that order. Because if you take c4 first, this will allow Black to move the pawn on c5 and something-something-“tempo”-something, with the result being that the knight is now entering the same color the queen is on before it moves.

Okay, that’ll do it! Easy enough, right? Okay, if anyone has any questions…

“You only gave two moves!” Uh, because that’s all Chess To Enjoy gave? This isn’t a mate-in-X problem; the stated objective was simply “White to play and win”. See, you’re supposed to figure out how you make the one little pawn slaughter this huge and terrifying yet badly positioned army, and once you’ve worked out “king takes knight”, “move the pawn one space”, and “take the further-back pawn first”, that counts as a job well done for the purposes of this problem.

“But what is the fewest number of moves possible??” Huh. Fine. 1.Kxe1 2.h3 3.h4 4.h5 5.h6 6.h7 7.h8=N 8.Nf7 9.Nd8 10.Nb7 11.Nxc5 12.Ne4 13.Nd6 14.Nxc4 15.Na5 16.Nxb3 mate. Just for the record, this requires a maximum of three moves without a pawn move or capture, so I’m understandably mystified as to where all this 50 move rule stuff is coming from.

“Doesn’t a serious problem require that the position be possible to arrive at legally?” Uuuuuuugggghhhh… :smack::mad: “Serious problem?” “Require?” Really? Really? Look at it! Look at the damn thing! There’s an ungodly mess of Black pieces piled in the lower left of the board, a single White pawn that somehow survived whatever it was that caused this, and a White king that just happened to find himself in the exact right spot to both prevent the Black knight on e1 from going anywhere and completely stuff the pawn on e2 so it can’t promote and unleash instant holy hell on the grossly overmatched monarch! This complete, colossal, royal clusterfrag is about as flippin’ serious as Deadpool doing a spoof of Last Week Tonight! Besides, you have any idea who Oscar Blathy was? His problems were flat-out nuts. That other problem of his in Chess To Enjoy is 247 moves (count 'em!). Expecting him to respect the time-honored strictures of blah blah blah is like expecting Tim Tebow to win a batting title. Jeez.

(Hey, is “opponent forced to make the same two moves over and over chess problem” actually a thing? Maybe I can find that king-and-pawns one where the White king has to cross the entire width of the board twice. That was another fun one.)

Yes, of course we’re overanalyzing the problem. That’s not because of anything in the problem; it’s because of us. Overanalyzing is something we do here, whether it’s about chess, art interpretation, or relativistic quantum mechanics.

I find it amusing that the post gently chiding us for “over-analyzing” is the one that is the longest and most analytical post of them all. :slight_smile: (It is complete, though. I forgot to mention the caveat about the order in which you need to take the pawns. Whoops.)

I thought it was more like overexplaining (which was intentional), but eh, one man’s meat.

Anyone know any good sites with problems like these? They really are fun to see in action, even if they’re not “serious”.

Hey, I did say it was it was “complete.” :slight_smile: It is the best response on the topic in this thread (IMHO), I just found it slightly amusing the way you characterized the other responses, before going into your own.

One thing that bugs me about this puzzle: Why does it start where it does? The first move is obvious even to beginners, even without thinking in any depth at all. What’s the point of a chess puzzle where the obvious first move is the correct one? Why not start the puzzle one turn later?

The only thing I can think of is that the puzzle creator found it amusing to start the board with Black’s entire army still in play, while White has only the barest minimum with which mate could be possible. But the elegance of that is severely diminished by having one member of Black’s unscathed army start the puzzle in unavoidable threat of capture.

I often recommend this site on the boards, but I really enjoy Tim Krabbe’s Chess Curiosities for this sort of thing. Sadly he doesn’t seem to update it any more, but there is lots of cool stuff in the Open Chess Diary section, plus a few other articles focussing on problems/studies. It’s all really well written, IMHO.

I think you’re right - the puzzle was more for ‘amusement’, as you say the easy key means it doesn’t rank with the world’s best.