Pandolfini's Puzzler #63: Two Knights In Shining Armor

Professor: Hello, Class. 

Class: Hello, Professor.

The class resounded as one, but very low.

Professor: Rachel, you wanted to show us a position?

Rachel: Nothing special. It came from the club ladder.

Professor: Wherever it came from, let’s see it.

Rachel went up to the demo board and set up the following position.

Question 1: How does White force mate in 2 moves?

Thomas:  I saw that. It was your game against Gandelbrot.

Lucian: Did he resign after you played your move?

Rachel: He knocked over his king and stormed off.

Lucian: That’s Gandelbrot!

Zephyr: I suspect he didn’t like those two knights.

Hale: If only Black didn’t have a bishop.

Thomas: And if it were Black's move . . .

Ryan: Then the position would be drawn.

Idris: In general, positions with just two knights are drawn unless there’s a mate set up and ready to be played.

Ryan: Sometimes the two knights can still win if the defender has a pawn move.

Zephyr: Then there'd be no stalemate after the defending king is cornered.

Lucian: But none of that applies to out first example.

Professor: Interesting. Let’s consider another two-knight position.

Question 2: How does White force mate in 2 moves?

Finding the answer to this one pretty quickly, the class spent the interim trading a few jibes.

Hale: It’s a kind of zugzwang.  

Lucian: Yes, but for these first two problems the defender has had few resources.

Thomas: Suppose you add stuff?

Professor: Fine. Let’s add a knight.

Question 3: How does White force mate in 2 moves?

The problem was solved instantly (by Zephyr, according to Zephyr), but it was hard to say who really got the right idea first.

Lucian: It's zugzwang. Problem 2 is like Problem 3. 

Zephyr: No, it’s more that Problem 3 is like Problem 2.

Hale: Is that what you mean by zugzwang?

Idris: But it’s not a true zugzwang, since it’s not reciprocal.

Zephyr: I had a premonition you’d say that.

Lucian: Professor, can you add more material than that?

Professor: Sure. Let's have Black be up by a double Exchange.

Zephyr: Something tells me White is going to win anyway.

Question 4: How does White force mate in 3 moves?

A minute is all the group needed. The only question centered on which knight to move first. 

Rachel: Let’s hear it for well-placed knights!

Zephyr: And poorly placed defending rooks!

Hale: We know about the advantage of two bishops, but the advantage of two knights?

Ryan: Let me put it this way: I don’t think so.

Thomas: May we see another position, please?

Professor: Okay, this time, Black has connected passed pawns on the 7^th rank.

Zephyr: Gee, thanks!

Question 5: How does White force mate in 3 moves?

The class stalled for a moment over the winning idea. Connected passed pawns on the seventh rank can do that to you. But the winning line was found, by Ryan and Idris, and the discontinuous discussion discontinued.

Lucian: Admittedly, I had to look twice at that one.

Zephyr: Are you sure it wasn’t three times?

Professor: I’m only sure that the next problem is our last for the day.

Question 6: How does White force mate in 6 moves?

The general idea was worked out smoothly enough, the main caution being the possible discovered check along the h-file. But the class got around that just fine, thanks to Zephyr. This time, she really did find the solution first. 

Lucian: A 6-move mate on question 6?

Zephyr: You have a problem with that?

Lucian: No, not even a question.

Zephyr: That's surprising, since I was the one who found the answer.

As the class came to an end, both Zephyr and Lucian tried not to smile.

Answers below. Try to solve NM Pandolfini's puzzles first!

Answer 1: Black is helpless after 1. Kh3. He can guard f2 or g3, but not both, and so the e4-knight mates next move.

Answer 2: White wins with 1. Nc6!, and there’s no way to stop a mating knight check from c3.

Answer 3: The killer move is 1. Kh8!

If the e7-knight moves, White’s f4-knight mates on g6.

If the c5-knight moves, White’s f4-knight mates on e6.

Answer 4: White mates in three moves by 1. Ndf6+ Kf8  2. Nh7+ Ke8  3. Nhf6 mate. 

Answer 5: The winning line is 1. Nd3+ Kd1  2. Kb1! e1/Q  (or any other promotion) 3. Nb2 mate.

Answer 6: The forced winning variation is 1. Nh6+ Kg7  2. Nf5+ Kg8  3. Nxe7+ Kg7  4. Nf5+ Kg8  5. Kg4! Nf8  6. Nxf6 mate.

Take note:

Starting from most natural positions, king and two knights cannot beat a lone king. The main difficulty is that one move before issuing mate the attacker would effect stalemate. That’s why, where feasible, the attacker tries to allow the defender to keep an extra pawn.

That way, stalemate is avoided by the defender being able to make a pawn move, even sometimes promoting the pawn in the process. But, obviously, this can be quite problematic. If you want to learn more about it all, various endgame texts deal adequately with such two-knight vs. pawn positions. A good presentation, for example, can be found in “Batsford Chess Endings,” by Speelman, Tisdall, and Wade (pages 112-115).