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Hnefatafl puzzle

Posted: Sat Sep 10, 2011 3:08 am
by crust
Since Hagbard and Adam were able to crack the last one, try this one for size....

Black to move. Only one move will save black from disaster - which move is it?

Use fetlar rules (king must be surrounded on 4 sides and cannot be captured on board edge)

I hope you find this puzzle REALLY difficult...!


Re: Hnefatafl puzzle

Posted: Sat Sep 10, 2011 1:26 pm
by crust
Greetings tafl boffins,

OK, so I just realised there are a couple of other solutions, too. Damn, must be getting old. Devising hnefatafl puzzles is harder than I thought! Well, let's see what you come up with, anyway. After a re-think, I make it five solutions in all. I wonder if anyone will get the full set. And I have to contemplate the possibility there may be other solutions I didn't think of. That's the wonder of hnefatafl, there's always a surprise lurking round the corner. Or usually IN the corner!
See you in the thunder dome.

Re: Hnefatafl puzzle

Posted: Sun Sep 11, 2011 1:19 pm
by Adam
My move is G4 to I4, as you need a piece on the third file to block I6. This plays out with black being able to defend both lower corners, though it seems easy enough for white to force a draw shimmying back and forth forcing black to defend open corners. Can't see how you'd prevent that. As for the other four, they all involve either blocking I6 or removing it, (h3 or h11 takes I6, though I'd leave h3 where it is, blocking k5 to to I5 looks good, as if the king takes you can block him in. I guess you 5th option is K4 to I4? But that would mean not having the option of taking out the guillotine easily.

So, is that the answer? Or is there a way of also preventing the draw shimmy?

Re: Hnefatafl puzzle

Posted: Mon Sep 12, 2011 11:47 am
by crust
Please note: an “x” after a move denotes that a warrior has been captured by that move.

Black’s problem is that White has a “guillotine” position – Black can't stop the white warrior on k3 moving to k2 and capturing his man on j2, and he also can't stop the same warrior from moving back to his original square on k3, opening a path for the king, which black [b:1v2hnq35]must[/b:1v2hnq35] block with another warrior if one is available, who will also be killed in his turn. So, Black has no choice but to go on feeding more warriors into this killing machine, while White calmly executes them until there are none left that can get there in time. This is the guillotine! It even has a realistic chopping action. Extremely nasty ... for Black (who often resigns at this point).

Good work Adam, you have identified all those solutions to this problem which concern dealing with that troublesome warrior on i6. He is the one who is preventing black from destroying the "guillotine" by moving j2 - k2 x (the "x" denotes that a warrior is captured, in this case, the "executioner" who is operating the guillotine) - if black makes this move before dealing with the warrior on i6 (either by capturing it or blocking it), then white can move the king forward i2 - j2, forcing black to respond with i1 - j1, and then that white piece on i6 sweeps down and captures with i6 - i1 x. And it's all over for black. So, neutralizing i6 is desirable. These are the ways it can be done:

h3 – h6 x (not brilliant as it leaves no black warriors on the 3rd rank)
h11 – h6 x (best)
k5 – i5 (blocking instead of capturing)
g4 – i4 (same idea)
k4 – i4 (the least good solution, as it makes it difficult or impossible to capture executioner)

THe continuation is as follows:
.................white k3 – k2 x,
black j6 – j2 x, white k2 – k3
black j2 – k2 x, white i2 – j2
black i1 – j1 (still looks o.k. for black!)

There is however another approach entirely, and another move you haven't thought of, and I have to confess it is that which I was thinking of when I designed this puzzle (later I realized that taking or blocking i6 would also work). This other move is cunning, and unexpected. It does not involve removing or blocking the warrior on i6. But what is it, you ask? Ah ha, I reply. So, the puzzle is not yet completely solved!


Re: Hnefatafl puzzle

Posted: Mon Sep 12, 2011 5:57 pm
by Adam
crust wrote:[This other move is cunning, and unexpected.
Ha, very cunning indeed! I figured it out right away after you indicated it was lateral thinking.

You can take advantage of putting the king in check to force him to move thus:

black b2 h2
white k3 k2x
black j6 j2 - king must move, and wherever he goes, black can then
k4 k3x closing the corner

A much better solution as black have a good chance of boxing him in.

Re: Hnefatafl puzzle

Posted: Mon Sep 12, 2011 8:15 pm
by crust
It is official, you are as cunning as a weasel!! That is exactly the answer I was looking for. If only I had designed the position to eliminate the other possibilities. Anyway, I remember using the technique of attacking the king to force him away from a guillotine - not always possible, but definitely a good idea in this case. b2 was nice and inconspicuous over there, it didn't look like it might rush in and attack like a berserker.

Now to come up with another...