Thursday, January 10, 2013

Devious chess tactic

White to move. How should white proceed?



Yancey Ward said...

It is devious, but not all that hard to find since the first two moves just seem like obvious beginnings for a tactic problem, even if you can't quite see the third move right from the start:

1. Rd6

Literally the first move I thought of- patzer sees exchange sacrifice, patzer plays exchange sacrifice:

1. .....c6 (or concede the piece)
2. Bd5 Kf6
3. Be3

The hard move to find. Threatens Bd4#, pins the knight to the a7 rook, and threatens to skewer the h8 rook if black opens a space at g5, or threatens to win at h8 if black plays Ke7. I don't really see a better defense than Kg7, and black will just lose the piece.

pht said...

1. Bd5+! Kf6
2. Be3!
Intending Rc4 next.
This must win a piece:

2. ... Be5/Kg7 (preventing mate threats)
3. Rc4
The knight is pinned against rook and falls.

2. ... Ra6 (trying to save knight)
3. Rc4 Be5/Kg7 (now enforced to prevent Bd4#, since knight has neither Nb3 Bxb3 nor Ne6 Bxe6.
4. Bxc5
up with knight in this line too.

Kerry Liles said...

Brute force.

Bd5+ wins at least a piece (the N)

pht said...

To Yancey Ward:
I may tell that starting with 1. Rxd6 was actually the first move I looked at too, after having found the idea to pin knight with Be3.

But then I found that:
1. ... Rxd6
2. cxd6
is rather meaningless since knight is now protected by the pawn, i.e. better protected than it was.

I can't see how you gain the knight with a black pawn on d6.

Then I thought:
What happens if I forget about Rxd6 and start with Bd5+ instead?

As far as I can see, that works nice, since the Bd6 will simply be overloaded, and black also missing a tempo, after:

3. Rc4
which wite of course white has to play before he can threaten Bd4#.
In your line, I think black has the tempo to play Ra6.

Have I totally misunderstood this?

By the way, is it really that hard to find the idea to pin knight with Be3?
I found that idea right away, and I'm really surprised to see only 3 answers here....

Yancey Ward said...


First things first, there is an error in notation on my solution, which you correctly deduced was supposed to be 1. ...cxd6 instead of 1. ...c6.

Secondly, my line doesn't win the knight- it pins it to prevent a defensive maneuver like 3. ...Nd7 or 3. ...Ne4:

1. Rd6 cd6 (or concede the piece)
2. Bd5 Kf6 (only move)
3. Be3

Pins the knight to the rook at a7 and threatens Bd4#. To prevent the mate, black must either cover d4, open a retreat square for the king by playing f4 or g5, retreat the king to g7 immediately so that he can play Kf8 in response to 4.Bd4+, or play Re7 or Re8 to plan to block the check from d4 with a rook. Every one of these will drop one of the two rooks and white wins a piece outright overall:

3. ....Nd7/Ne4/Ne6
4. Ba7 wins a piece;

3. ....f4/g5
4. Bd4 Kf5/Kg6 (only moves respect)
5. Bh8 wins a piece;

3. ....Re8
4. Bd4 Re5
5. f4 wins a piece, or better for white 4.Bg5! is simpler;

3. ....Re7
4. Bd4 as immediately above.

Now, I think your beginning line does win, though I must admit I never even noticed it the other day. However, in looking at it this morning, I do take some issues with your continuations afterwards. Let's take it from the top:

1. Bd5!? Kf6 (Ne6 loses immediate)
2. Be3! Ra6

The better defense seems to be Raa8 to me, but I might be missing something in that line- I am just not completely sure. However, let's continue with your main line:

3. Rc4?!

Here, 3.Bc4 attacking the rook at a6 wins instantly since white also is threatening Rd6 transposing into a variation of my line above. With Rc4, white loses a tempo. While not giving up the win, it is clear to me it is not nearly as decisive as the my line above since all I can find is white winning an exchange overall:

3. .....Ne6!
4. Bb7

Not 4.Be6: [4.Be6? Ke6 5.Bd4 Kd5! and the rook at c4 has become a liability]. Continuing:

4. .....Raa8
5. Ba8 Ra8 and white has the exchange.

Before I close, let's just outline what I see in the line 2. ...Raa8:

1. Bd5 Kf6
2. Be3 Raa8
3. Ba8 Ra8

Also wins the exchange. Where I can't quite decide here is what happens if white doesn't grab the rook at a8? Not sure 3.Ba8 is the best move. Very complicated.

pht said...

OK, I see things that I have overlooked:

1. Bd5+ Kf6
2. Be3 Ra6/Raa8 (lifting pin on the knight)
3. Rc4? Ne6!
Since Re1 is temporarily hindered by bishop on e3 (not moved to d4 yet, only planning to), so black can answer Bxe6 with Kxe6. I missed that.

As allways, I have analyzed in head only (never use a board for analyzis).

I conclude that I found the right basic idea, but that it was more complicated than it seemed to me.

Yancey Ward said...


For doing it in your head, you do very, very well- much better than I can do, I think. I am limited to about 3 or 4 moves deep before I start making really egregious errors. I always try to do it in my head first, but before I write a comment, I double/triple check it with my board.