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June 11, 2016

Saturday Afternoon Chess/Open Thread 06-11-2016 [OregonMuse]


Benjamin_Franklin_playing_chess.jpg
Lady Howe Mating Benjamin Franklin - Edward Harrison, 1867

I have no idea who that light-in-the-loafers guy standing between them is. He appears to looking down at an 18th century iPad. Perhaps he's analyzing the game with one of his chess apps.

“Chess teaches foresight, by having to plan ahead; vigilance, by having to keep watch over the whole chess board; caution, by having to restrain ourselves from making hasty moves; and finally, we learn from chess the greatest maxim in life - that even when everything seems to be going badly for us we should not lose heart, but always hoping for a change for the better, steadfastly continue searching for the solutions to our problems.”

--Benj. Franklin

Some Unfinished Business

Here is one of last week's problems:


20160611 - Unfinished business.jpg

It was White to play and mate in 2. The answer is 1.Qe5! which threatens mate by either Qb8 or Qxh8, and Black can't defend against both. The question came up whether Black could escape by castling, that is, 1... O-O. Normally, castling legality is notated in the FEN string, except that in this case, the FEN string was derived from me setting up the position in Chessbase, and whatever the default was, that's what was written in the FEN.

So in response to inquiries, I felt obliged to cover my pasty white butt by saying you need to assume that castling is not possible. 1...O-O is a cook to the problem made possible by my sloppiness. But then, a later commenter on the thread (thank you, 'Fischer') noted that my instruction wasn't necessary, and that the legality of castling can be determined just by looking at the position. In other words, everything you need to know to be able to make the determination is right there in the position, even without an FEN string.

So I thought I'd pose this question to you all, is castling legal in this position or not? I'll provide the answer below the fold. But you can swipe the next line past the word 'Hint' if you would like one, and I'll give a mate-in-1 to look at before we dive beneath the fold.

Hint: Consider Black's last move.

White Mates In 1


20160611 - Mate in 1.jpg
FEN: [r1bqkb1r/pp1npppp/2p2n2/8/3PN3/8/PPP1QPPP/R1B1KBNR w KQkq - 0 1]


About The Painting

From an article on Ben Franklin and chess:

Franklin was brought into peace negotiations with Rear Admiral Viscount Howe thanks to chess. In late 1774, although he had not yet met Lord Howe, Franklin received an invitation to play chess with the gentleman’s sister. Franklin later wrote that after playing a few games with her, he decided to meet Lord Howe at her house to avoid “speculation,” as “it was known we played together at chess.” In fact it appears that the games of chess had been a lure intended to bring Franklin into discussions with Lord Howe, as she used the playing sessions as an excuse to effect an introduction between the two for that purpose.

Unfortunately, even though Franklin is well-known as an avid chess player, none of his games have survived, if any were recorded.


Concluding The Unfinished Business

In order to determine if castling is legal or not, we need to find out if any of the conditions governing castling have been violated. The only ones that apply are the "move" rules, that is, if the King or Rook have moved, castling is no longer allowed. So, looking at the position, can we determine if either have moved. Since the problem specifies that it's White's turn to move, what was Black's previous move? We know that it couldn't have been a pawn move, since both remain on their home squares. Therefore, Black's last move had to have been with either the King or the Rook. But if that's the case, castling is now no longer possible. So 1.Qe5! is still the valid solution, and the reply 1...O-O is illegal. QED.

There is a whole sub-genre of chess problems, called 'retro puzzles', where you are given a board position and you are to determine how that position came to be, just from deductions you can make from it. Here's an example:


20160611 - Find preceding moves.jpg

The only instructions I have for the puzzle is "How did this position come about?" and "Find the preceding moves." It doesn't say whose move it is, or how far back you have to go. Presumably, you'll be able to answer those questions after you study the position for a while.

I simply cannot wrap my head around these 'retro' chess problems, but I was able to solve this one, so it must be pretty basic. I only had to come up with two moves by White and one by Black to arrive at the published solution.


White Mates in 3

A straightforward problem:


20160611 - White mates in 3.jpg
FEN: [1q3rk1/5ppp/4n3/R2N4/8/3Q4/5P2/6K1 w - - 0 1]


White Mates in 4

This one looks like one of those games where Black gets into trouble early on and his King gets chased out into the open. You can see, if you do an inventory of the pieces, that White is down a bishop. He probably sac'ed it a few moves earlier to pry the black King loose from safety.


20160611 - White mates in 4.jpg
FEN: [rn1q1bnr/1b2p1pp/p7/1pp1N3/3kP1Q1/8/PP3PPP/RNB1K2R w KQ - 0 1]

I think this one is going to be tough for most of you. And the reason is that the first move isn't real obvious. In fact, if I were to tell you what it is, you'll probably say, "Why is *that* move the correct move?" At least that is what I told myself when it was first shown to me. So no, I didn't figure this one out for myself (*hangs head in shame*), I had to have it explained to me by my chess app. But I really like this problem because even though it doesn't look forced, it actually is, pretty much.

My only advice is to look at the board carefully for White's threats and potential threats, i.e. what's the most efficient way to bring the king hunt to a successful conclusion.


Endgame Of The Week


20160611 - Endgame.jpg
FEN: [8/8/8/3R4/2K5/6pp/k7/8 w - - 0 1]

Looking at this endgame position you'd probably think there's no way White is going to be able to stop those connected passed pawns. And that's a reasonable assumption because in most cases, two connected passed pawns on the sixth rank will pretty much guarantee a win. But not this time. In this position, Black's King is completely misplaced, and that allows White to eke out a victory. So, find the win by White against Black's best opposition.

It is not necessary to play it out to the actual checkmate, just show how White can achieve clear superiority.


___________

Problem solutions will be posted as an update in the fullness of time.

___________

[Solutions Update]

The fullness of time has now arrived:


1. White mates in 1

1.Nd6#

Some of you morons might have been tempted by 1.Nxf6+, but Black then replies 1...Nxf6, and there goes your mate in 1.


2. Retro problem

As I said, I'm lousy at these type of problems, but this is how I managed to solved this one: I saw that Black is in check, therefore it is his move. Then I thought hmmm, how then did White put him in check? The position of the bishop in the corner means that White could not have moved it there as a checking move. So I thought that there was probably another piece somewhere on the a1-h8 diagonal that was removed to create the check. But what? The pawn on e6 suggests it has been involved in some sort of capture, and so I asked myself, what would a previous en passant capture have looked like? In order for a pawn to have ended up on e6 after an e.p. capture, it must have started out on d5. Which means that the captured Black pawn had to have started out on e7. But in order for the Black king not to have been in check throughout all of this, the White pawn must have first been on e4, blocking the a1 bishop from giving check. So the board position must've looked like this:


20160611 - Find preceding moves orig.jpg
FEN: [8/3Kp3/5k2/8/3P4/8/8/B7 w - - 0 1]

And to get to the original diagram from the above diagram, here are the moves:

1.d5+ e5
2.dxe6+ {and there's your en passant capture}

Some of these retro problems get fiendishly complicated with lots of pieces on the board in all sorts of weird positions, and there's no way my tired old brain can work through all of the convoluted threads of logic and deductive reason in order to reconstruct the position from previous moves. And some of the retro problems only show the pieces in one color, so you've got to figure out which pieces belong to White, and which pieces belong to Black. AAAAAGGHHH!


3. White mates in 3

The decision tree for this problem is a straight line: 1.Ne7+ Kh8 2.Qxh7+ Kxh7 3.Rh5#


4. White mates in 4

This is going to be fun. White's first move is...

1.Qf4!

...and you're probably thinking "Wha..?" If you're not, if you can see what's coming, good for you.

This move doesn't do anything directly by itself, it just creates a threat, i.e. it's sort of a zwischenzug. The threat is blunt: 2.Be3#. This threat didn't exist last move because the knight on e5 was hanging. So with White's first move, he prevents Black from escaping the mating net by taking the knight.

So now Black is in a pickle. Any move he makes to bring some pieces into the fight, such as 1...Nf6, or 1...Nc6 fail, because of 2.Be3#. In fact, the *only* move available to Black to counter the immediate mating threat is 1...Qa5+.

Which White defends with:

2.Nc3

Black is now forced to capture in order to stave off the impending checkmate:

2...Qxc3+

And then the rest is mopping up:

3.bxc3+ Kxc3
4.Qd2#


5. Endgame

As I mentioned, the Black king is horribly placed. White can use this to create mating threats that will allow his King to scoot over to the king's side and snarf those pawns. It's a bit complicated;

1.Rd2+ Kb1

If 1...Ka1? 2.Kb3 and Black cannot prevent 3.Rd1#

2.Kc3 Kc1

If 2...g2, then 3.Rd1+ Ka2 4.Rg1 h2 5. Rxg2+ and Black is done.

3.Ra2 Kd1

If 3...Kb1 (this is what my chess app thought was best), then 4.Re2 g2 5.Re1+ Ka2 6.Rg1 h2 7. Rxg2+ as above.

4.Kd3 Kc1

If 4...Ke1, then 5.Ke3 Kf1 6.Kf3 and Black can't advance the pawns thanks to Ra1#, so White eats them, e.g. 6...Kg1 7.Kxg3, etc.)

5.Ke3 h2

or 5...g2 6.Kf2 Kb1 7.Re2 Kc1 8.Kg1

6.Ra1+ Kb2
7.Rh1 Kc3
8.Kf3 1-0


___________

Note: that cryptic line of letters and numbers you see underneath each board diagram is a representation of the position in what is known as "Forsyth-Edwards Notation", or F.E.N. It's actually readable by humans. Most computer applications nowadays can read FEN, so those of you who may want to study the position, you can copy the line of FEN and paste into your chess app and it should automatically recreate the position on its display board.

___________

So that about wraps it up for this week. Chess thread tips, suggestions, bribes, rumors, threats, and insults may be sent to my yahoo address: OregonMuse little-a-in-a-circle yahoo dott com.

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posted by Open Blogger at 05:42 PM

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