Friday, February 21, 2014

Challenge yourselves: Rook vs 4th rank pawn + Rook

Not long ago we saw how to set up (and how to prevent) a Lucena Position when your pawn is on the 5th rank. Today let us move that pawn back by one rank and see whether it will make a difference:

White to move, can he win?

If you've read through the previous articles regarding the pawn on the 5th rank, you should know that White will wish to attain a winning position by the time he pushes his pawn to the 5th rank (of course if you've forgotten what are conditions for a win to occur with the pawn on the 5th rank, here goes: http://www.nushsblackknights.blogspot.sg/2014/02/rook-5th-rank-pawn-vs-rook.html).

The factors that act in White's favour:

  1. Black's king is cut off from the enemy pawn
  2. Black's king is on the Long Side of the Board, which by now you should know is a disadvantage for the weaker side

But Black also has one major plus which makes the problem very tricky for White: White's pawn is on the 4th rank, not the 5th. Which means that all the guidelines we have learned regarding the long/short sides of the pawn and the position of the kings won't hold true in this position!

So let us see whether you are able to uncover the secrets behind this interesting position. Once again, you can experiment by placing the kings, rooks and pawn in various positions (so long as the pawn is on the 4th rank and no pieces are on the verge of capture!) and see whether you can discover some interesting patterns.

Have fun, guys!

Wednesday, February 19, 2014

Performing the 2 bishops checkmate: A revision

I realize that some of us are still not familiar with the 2-bishops checkmate, even though we have tried and practiced it many times together. For example, if you're given the random position below:

White to play and win

Can you execute the entire checkmate procedure for White?

Many of us will be quite well versed with the initial stages of the checkmate-- using the 2 bishops to fence off the enemy king-- but when the Black king is finally driven to the side of the board, that's where we often slip and end up letting the king escape (or worse still, stalemating by accident).

While the 2-bishops checkmate is not common in actual tournament play, it is still quite easy to learn; in contrast, the incredibly rare bishop-knight checkmate is not easy to master, and even grandmasters have been known to botch up such positions. That's why many trainers do not recommend learning the bishop-knight checkmate (though you can always learn it for your own pleasure) but they do not mind teaching their students this interesting double-bishop maneuver.

So take this as a revision, and let's go through the steps again.

Part 1: Driving the king to the side of the board

You will find the first part of the checkmate quite easy: Use the two bishops to create a "box" and fence off the enemy king, while at the same time using your own king to protect the bishops. Then slowly shrink the "box" (similar to the procedure in the common queen/rook checkmates) until the opponent is driven to one side of the board. So from our initial position, the game may continue something like this:

1. Kf7 Kc5
2. Be5 Kc4
3. Be4 Kc5
4. Ke6 (D)

Working together to create the "box"

Notice how the 2 bishops work together to create a barrier which the enemy king cannot cross. The White king also steps forward to protect both bishop, making them immune to capture. The rest of the "shrinking" procedure should be quite intuitive by now: See the KnightVision viewer below if you still need help in visualizing:



Part 1 accomplished

Black has been driven to the side of the board. Now White must proceed to Part 2: Forcing Black to the corner where checkmate will be delivered.


Part 2: Forcing the enemy king to a corner

In order to execute the checkmate the Black king must be forced into one of the 4 corners of the board. Be careful: Here's where many of the stalemate dangers come in, and if you fumble the win will slip away from your hands!

The trick to completing this seeming difficult mission lies in two simple concepts: (1) Using the bishops to removes squares of access from the enemy king, and (2) exploiting king opposition similar to the standard rook/queen checkmates.

Returning to the original position, we see how this is executed:

16. Bc2 Kf1

White removes the d1 square from Black and forces him to the h1 corner

17. Bd2 Kg1

Removing the e1 square and forcing Black even further in.

18. Kg3

Utilizing the concept of king opposition to keep Black's king on the 1st rank. If 18. Bd3 then Black escapes with 18... Kh2.

18... Kf1

If 18... Kh1 then White delivers the checkmate with 19. Bd3 Kg1 20. Be3+ Kh1 21. Be4#. But be careful over here: Do not mess up with the tempting 19. Be3?? (trying to remove even more squares of access) which leads to immediate stalemate. Keep your eyes peeled for these dangers!

Now, the rest of the checkmate is easy:

19. Bd3+ Kg1
20. Be3+ Kh1
21. Be4#
1-0

Checkmate



Go through the steps for Part 2 again, and make sure you're familiar with the mating technique and the accompanying drawing traps.


Part 3: Triangulation/ waiting moves

If you were observant enough, you would realize that in Part 2, White was able to successfully execute the 16. Bc2 maneuver because the White king happened to be on e1. But what happens if somehow after Part 1, you end up in a position like this:

White to play: What's happening?

And now White can't perform the Bc2 maneuver because Black's king is on d1! So how can White continue in this position?

1. Bf1 is clearly not the way to go, since it allows Black to escape with 1... Kd2. But there is one more hidden trick which White can use, and if you understand the concept of triangulation, you will be able to see the next move.
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1. Ke4! Ke1
2. Kf4 Kd1
3. Kf3 Ke1

And suddenly we come back to the position we saw earlier in Part 2, where Black's king is on e1 and now White can perform 4. Bc2. These series of mysterious king moves are what is known as triangulation, where White makes waiting moves with his king (and exploiting the fact that his opponent only has two free squares to move on) in order to get the Black king to the desired position.

Another position which you may run into is this one here:

White to play; be careful!

Where White is only a few steps away from checkmate. Over here, don't be a dunce and throw away the win with 1. Be3 stalemate! Rather, a simple waiting move-- for example 1. Bd3, forces the Black king to get into the desired mating position: 1... Kg1 2. Be3+ Kh1 3. Be4#

In Part 2 of the checkmate, we should always be on the lookout for stalemate traps, and exploit triangulation and waiting moves in order to avoid them.

...

So to sum up, the stages for successful execution of the double-bishop checkmate are as follows:

  1. Use the 2 bishops to create a "box" that fences off the opposing king.
  2. Slowly shrink the box to drive the opposing king to a corner of the board, at the same time using your king to protect the 2 bishops.
  3. Once the enemy king is at the side of the board, use the bishops to cut off squares of access and exploit king opposition to drive the enemy king to the corner. Just make sure not to cut off too many squares and end up stalemating the opponent!
  4. If necessary, waiting moves might be required in order to prevent stalemate from occurring.

Now that was easy, wasn't it? If so then try setting yourselves a personal challenge: Try to perform this checkmate with less than 5 minutes on your clock (which should actually be a no-brainer once you're familiar with the procedure). Once you've done that, shorten the time to 2 minutes; your ultimate goal will be to successfully execute the checkmate within less than a minute (:

Tuesday, February 18, 2014

Rook + 5th rank pawn vs Rook

Yesterday we looked at the challenge I issued on Friday (Rook + 5th rank pawn vs Rook) and the methods which both sides use to force a win or a draw.

White to move, can he win?

To repeat again, these are the goals which both sides hope to achieve:


  • Black wants to get his king in front of the enemy pawn, thus making it possible for him to create a Philidor Position and drawing the game
  • White wants to prevent Black's king from getting in front of his pawn, by using his rook to cut the enemy king away from the battle. This makes it easier for him to create a Lucena Position, which will win for White.

(Once again if you still have no idea what a Lucena/Philidor Position is, or need revision on basics, I'll place this here for convenience: http://nushsblackknights.blogspot.sg/2013/12/revising-basic-rook-endgames-part-1.html)

Though it may seem tedious to calculate all the variations, there is fortunately for us a simple guideline when it comes to combating a pawn on the 5th rank: The stronger side wins only if the weaker side's king is cut off by one or more files on the long side of the board, or two or more files on the short side of the board. This guideline is mostly true for central, bishop and knight pawns on the 5th rank (save a few exceptions we will look at later); as usual, rook pawns form exceptions and we'll discuss them in the last part of this article.

If you're confused over the term "long side of the board", the following diagram will help to clarify:

Yellow: Long side. Green: Short side

The long side of the board (the yellow squares in the diagram above, from the a to d-files) is the side of the board with the greater number of squares between the pawn and the side of the board. Conversely, the short side of the board (green squares, f to h-files) is the side with the smaller number of squares. So if the pawn were on f5 rather than e5, the long side of the board will be the a to e-files, while the short side will be the g and h-files.

In such positions where the weaker side's king has been cut off by the enemy pawn, he should strive to place the king on the short side of the board; the reason being that his rook wants to rain checks upon the enemy king from the longer side of the board (remember that rooks are strongest when far away from the opponent's king!) and of course the king should not get into the way.

Part 1: The long side of the board

Let's return to the position we saw earlier and see how this works out:

White to move, can he win?

And now it should be quite clear that White can win, because Black's king is cut off on the long side of the board. Thus Black cannot use the rook-checking trick to force a draw, because his king gets in the way and the short side of the board is-- well, as its name suggests-- too short for the rook to check safely.


The outcome is still the same whichever side it is to move, so for clarity's sake we'll give White the move here:

1. Kf5

Exploiting the short side of the board, and preparing the advance the pawn

1... Rf8+

If Black tries to check on the short side of the board with 1... Rh8, then after 2. e6 Rh5+ 3. Kg6 Black can no longer check safely, and soon falls to 3... Rh2 4. e7 Rg2+ 5. Kf7 Rf2+ 6. Ke8 with a Lucena Position in White's favour.

The attempt to check on the long side of the board also fails because Black's king and White's pawn get in the way: 1... Ra8 2. e6 Ra5+ 3. Kf6

2. Ke6 Re8+
3. Kf6 Rf8+
4. Ke7

Chasing away Black's rook and allowing the pawn to advance again

4... Rh8

Once again we see that after 5... Rh7+ 6. Kf6 Rh6+ 7. Kf7 Rh7+ 8. Kg6 Black's rook can no longer keep up the rain of checks

5. e6 Rh2
6. Kf7 Rf2+
7. Ke8 Kc7

The variation 7... Rh2 8. e7 Rh8+ 9. Kf7 Rh7+ 10. Kf6 Rh6+ 11. Kg7 also loses for Black. Hopefully by now you are familiar with how the Black rook's checking ability is crippled when on the short side of the board.

8. e7
1-0

Reaching a Lucena Position, with a win for White.

...

So that looked simple enough. But now let's see how even the smallest change to the initial position can make things very different!

Can White still win here?

Black's king still appears to be cut off by the enemy rook, but in fact he is not because Black has a special move at his disposal: Rd8, where after trading rooks Black's king forces its way to the front of the pawn!

In such a position the outcome of the game is decided by not whether a Lucena/Philidor Position can be reached (because the rooks have already been traded!) but rather which side has the opposition. I leave the remainder of the analysis as a very simple challenge to y'all: Can White win if he has the move, and will the outcome be different if Black had the move instead?


Part 2: The short side of the board

So how does the weaker side draw when his king cut off by only one file on the short side of the board? Let's take a look:

Draw regardless of who to move!

So let's say it's White to move, and he tries to perform the same trick of using the king to help advance the pawn. Since the close proximity of the Black king prevents White from using the f-file, the game may continue along the lines of:

1. Kd5 Ra8

And now Black threatens a barrage of checks from the long side of the board. This time, unlike our first example, White cannot run away from the checks!

Attempting to force the king away with 1. Rg1+ leads to 1... Kf7, allowing the Black king to get in front of the pawn and paving the way for a draw. Notice that if the Black king were on g5 rather than g6, then 1. Rg1 will have very different results altogether... which we will see later on. Lets concentrate on the current position first.

2. e6

Once again, attempting to block the checks with 2. Rc1 fails to 2... Kf7

2... Ra5+

There is no way White can run away from the checks now because Black's rook is sufficiently far away. So for example the game can continue something like this:

3. Kd6 Ra6+
4. Kd7 Ra7+
5. Kc8 Re7
6. Re1 Kf6
1/2-1/2

Piling up upon the e6 pawn and winning it, thus simplifying to a rook vs rook draw.

...

So as I mentioned earlier, why will things turn out differently if the king were on g5 rather than g6? Let's take a look:

White to move wins

If it were Black to move he will just play 1... Kg6 turning the position into the drawn game we saw earlier. But if we give White the move:

1. Rg1+!

And now Black's king cannot step in front of the pawn because the White pawn covers the f5 square.

2... Kh5
2. Kf5

With Black's king cut off by two files, White can safely step onto the f-file where it is immune to checks from the long side of the board. The rest of the game is easy:

2... Rf8+
3. Ke6 Re8+
4. Kd6 Rd8+
5. Ke7 Rd2
6. e6 Re2
7. Kf7 Rf2+
8. Ke8 Re2
9. e7 Rd2
1-0

Creating a winning Lucena-like Position for White. Note that it isn't exactly a Lucena Position because White's king is on h5 and prevents 10. Rg4, but after 10. Rf1 Kg5 11. Kf7 Black can no longer check safely and the pawn is free to promote.


Part 3: Rook pawns

As I have stated earlier rook pawns always form special exceptions to general endgame rules, and so we'll see how different they are in this position.

No win for White over here!

A quick look at the position should be enough to tell that this is a dead draw: With the pawn huddled in a corner White can never hope to step forward to support the pawn. Both 1. Rc1+ and 1. Kb4 (attempting to step out to help the pawn) fail to 1... Kb7 where Black's king gets in front of the pawn with a draw. And with rook pawns, there is no other side (no short side this time!) for the White king to step onto.

If you fancy another challenge, you can work out how many files does the Black king need to be cut off by in order for the game to be a win for White. (Perhaps this link to one of our earlier topics may help: http://nushsblackknights.blogspot.sg/2013/12/a-lucena-with-rook-pawn.html)


Summary

Was that too many examples for y'all to absorb? If so, then let us summarize things to make our understanding easier:


In this rook + pawn vs rook position where the pawn is on the 5th rank, the stronger side can win if:

  • The weaker side's king is cut off by at least 1 file along the long side of the board. This prevents the weaker side's rook from forcing a draw through repeated checks, as the short side of the board is not long enough to do this safely and the king gets in the way on the long side of the board
  • The weaker side's king is cut off by at least two files along the short side of the board. If the weaker side's king is too close, then the stronger king is forced to step onto the long side of the board and expose himself to enemy rook checks.
  • If the weaker side can get his king in front of the stronger side's pawn, then his chances of drawing becomes much higher.

This can be summed up into the simple guide which holds true for most cases: A win is more likely with the weaker king on the long side, while a draw is more likely on the short side (or with the weaker king in front of the pawn). Of course, we must note down the important exceptions to this rule, as we have investigated in the examples earlier.

Steady on, my brothers. The journey will get even tougher as we progress deeper into the mysteries of rook endgames.

Sources:
"Silman's Complete Endgame Course" by Jeremy Silman

Friday, February 14, 2014

Challenge yourselves: Rook + 5th rank pawn vs Rook

In most rook endgames where one side is a pawn up, both sides will want to simplify to a basic endgame position which can be easily handled. For the stronger side, he will want to achieve a win by creating a Lucena Position, where the "building a bridge" maneuver will help pick up the point. For the weaker side, his saving grace will be a Philidor Position, where the barrage of rook checks will prove too much for the stronger side to handle.

Rain! Let it rain!

And please, do tell me that you remember how to play both the Lucena and Philidor Positions! These basic skills should by now be firmly ingrained in your mind. If not... sigh: http://nushsblackknights.blogspot.sg/2013/12/revising-basic-rook-endgames-part-1.html

So now let us take a look at how we can apply this when we take a step back, and look at a rook endgame with the pawn on the 5th rank:

White to move, can he win?

It should be clear by now that in this kind of position, both sides have their own desired outcomes:

  • Black wants to get his king in front of the enemy pawn, thus making it possible for him to create a Philidor Position and drawing the game
  • White wants to prevent Black's king from getting in front of his pawn, by using his rook to cut the enemy king away from the battle. This makes it easier for him to create a Lucena Position, which will win for White.

Of course the burning question that everyone wants to know is... can either side achieve their objective? That will be for you to find out!

Once you've cracked the puzzle, you can also take a look at the following two positions (both White to move) and see whether the result is a win or a draw:

Shouldn't be much of a difference?

Or perhaps not...?

In fact, you can even play around with the positions of the pieces (just make sure the pawn is on the 5th rank, and both kings aren't under attack) and experiment to see how a Lucena or Philidor position can be achieved under varying circumstances. Who knows, you might even discover some trends...

But that, of course, is up to you to stretch your own mental limits. Experiment, explore, excel, and have fun trying!

Sources:
http://www.moddb.com/mods/project-raptor-the-foxtrot-code/images/artillery-barrage

Wednesday, February 5, 2014

Passive rooks shall stay passive

So not long ago I issued the 2nd LNY challenge, and I present it here again in its full glory:

White to move: Can he win?

The answer, as most of ye have pointed out, is NO. The unfortunate position of White's rook, Black's active rook, and the fact that White's king is away on a holiday is enough to save half a point for Black.

But here's the interesting bit: Black draws not because he can keep his rook behind White's pawn (as some of you have pointed out), in fact if he follows the same method the game will end in a win for White.

Rather, Black draws because he can set up a Vancura Position, which is a draw for the weaker side. You didn't think I was going to let you get away reading through and forgetting all our previous content, yeah?

So first of all, let's see why Black cannot win if he lets his rook stay behind the pawn:


The main reason why this position is different from the one we saw in our previous article (with the pawn on h7), is because the White king now has a shelter on h7 which will prove useful to him. White wins by slowly marching his king towards the g-file, making sure that he stays on the first and second ranks to make sure Black doesn't seize control of that file. Once he has reached the g-file, he can then then march up the file to make contact with his pawn, before exploiting the shelter on h7 to escape from the rook check (which would not have worked had the pawn been on h7) and free his rook from its passive slumber.

1. Kc2 Rh3
2. Kd2 Rh2+
3. Ke1 Rh1+
4. Kf2 Rh5
5. Kg3 Rh1

Stage 1 is complete: White's king has reached the g-file. Now he slowly walks towards his pawn

6. Kg4 Rg1+
7. Kf5 Rh1
8. Kg6 Rg1+
9. Kh7

Stage 2 is complete: White tucks his king away safely on the h7 square, and his rook prepares to step out. The rest of the game should be easy by now:

9... Rc1

Desperate counterplay since staying on the g/h files allows Rg8 followed by Rg6, allowing White's king to step aside and let the pawn advance.

10. Rf8 Rc6

10... Rc7+ 11. Kg8 Rc1 (preparing 12... Rg1+) 12. Rf7+! also loses quickly for Black

11. Rf7+ Kb6
12. Kg7 (D)
1-0

A free road for the pawn

So now we see why letting the rook stick behind the pawn is no longer effective for Black in this case. But he still has one more weapon hidden under his sleeve, which we have all looked at not long ago: The Vancura Position.

Returning to the original position, we can now see that Black can easily force a draw by setting up a Vancura Position:

Black finds the correct method to draw

1. Kc2 Re1!

Or 1... Rf1/Rg1. The purpose is the same: To leap to the 6th rank where Black can tie down the pawn and deny the White king passage to the h7 square.

2. Kd2 Re6

Of course if 2. a7 Black simply draws by returning to the h-file with 2... Rh1

3. Kd3 Rc6 (D)
1/2-1/2

Looks familiar?

With a Vancura Position, and a draw. And if you've forgotten how to handle this position, well... here goes: http://nushsblackknights.blogspot.sg/2014/01/the-vancura-position.html

...

So that was easy... but some of you might be wondering, does this still apply if the pawn is not a rook pawn?

White to move: What happens now?

This time Black cannot hope to draw by setting up a Vancura Position, because the White king can seek safety on h6 (see the KnightVision viewer below for easier visualization):

1. Kc2

Of course 1. g7? Rg2+ is a draw

1... Re1
2. Kd2 Re6
3. Kd3 Rc6

Attempting to stall White's king march by shuffling along the e-file will only free the White rook from its position: 3... Re1 4. Rf8

4. Ke4 Rc4+
5. Kf5 Rc5+
6. Kg4 Rc6 
7. Kh5 Rc5+
8. Kh6
1-0

Hiding from the rook checks, and unleashing White's rook into the fray.

So is this a losing position for Black? The answer is NO; even though the Vancura Position does not work here, the pawn on g6 is closer to Black's king than the pawn on h6, so Black can (surprisingly) draw by moving his king towards the pawn!

1. Kc2 Kc7!
2. Kd2 Kd7

Marching slowly towards the prized target on g6, while keeping the rook behind the pawn; although this fails with a rook pawn, it surprisingly works for a non-rook pawn!

3. g7

If 3. Ke2 Black will proceed with Ke7 followed by Kf7, picking off the pawn

3... Ke7
4. Ra8

Played along the same lines as the tactical trap with the pawn on h7; but this time, White cannot hope to exploit the skewer because the enemy king is too close to the pawn.

5... Rxg7
5. Ra7+ Kf8
1/2-1/2


So we can take away three simple learning points from this article:

  1. In a position with a rook pawn on the 7th rank, the stronger side's rook in front of the pawn and the stronger side's king too far away to help, the weaker side draws by shuffling his rook behind the enemy pawn. However, care must be taken not to fall for any tactical traps!
  2. In a similar position but with the rook pawn on the 6th rank, the weaker side draws by setting up a Vancura Position.
  3. In a similar position but with a central pawn instead of a rook pawn, the weaker side cannot draw by setting up a Vancura Position; however, he can draw by rushing his king to the pawn in order to pick it off.

Of course, all these is thanks to the passive position of the stronger side's rook, and the active position of its weaker counterpart.

By now you should be quite familiar with most of the rook endgame basics, so absorbing these should not be much of a problem for y'all.

Links:
The Vancura Position: http://nushsblackknights.blogspot.sg/2014/01/the-vancura-position.html
Passive rook + Pawn on 7th rank (Part 1): http://nushsblackknights.blogspot.com/2014/02/2nd-lunar-new-year-challenge.html

Source:
"Silman's Complete Endgame Course" by Jeremy Silman

Sunday, February 2, 2014

2nd Lunar New Year Challenge!

In Part 3 of our revision on basic rook endgames (http://nushsblackknights.blogspot.sg/2013/12/revising-basic-rook-endgames-part-2.html) we talked about how Tarrasch's Rule applies when it comes to the escorting of passed pawns. So to revise again we see the importance of this rule in the following position:

White takes the point regardless of who to move

Where we see the dead-easy win for White: Kc6 followed by Kc7 chasing away the Black rook, whose blockade of the White pawn is all but imaginary.

But if we switch the position of the rooks:

No win over here!

Then White's mighty pawn is suddenly reduced to a helpless weakling! Once again we see the importance of putting our rook behind a passed pawn (regardless of which side it is on): All Black has to do is to shuffle along the h-file and tie down the White rook to defending the pawn; if the White king tries to make contact with his pawn with Kg6 Black just kicks him away with a rook check on the g-file.

One important exception to note in this position, however, is that the h5 square is off-limits to Black: 1... Rh5?? 2. Kg6!. White's king touches his pawn and attacks Black's rook at the same time, thus Black cannot check safely on the next move. White can then free his rook and win the game. Keep your eyes peeled for these hidden tricks!

Another trap to look out for, is the tempting move 1... Kc7?? (intending to march towards the White pawn and pick it off). Can you see the tactical bomb for White?

White to move and exploit Black's terrible blunder
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2. Ra8! threatening promotion, and if 2... Rxh7 White wins the rook with the skewer 3. Ra7+. Many players have fallen for this trap, so watch out!

So with these in mind, I thus issue a second challenge for y'all to try during the rest of the LNY break. Here it is:

White to move: Can he win?

I think I've given you quite a lot of help with the info above, so by now it should be obvious that pushing the pawn to a7 will result in an immediate draw (so long as Black does not fall for any of the traps I've mentioned above!). So the question is: If White doesn't push the pawn, can he still win this game?

The answer lies in your hands. Have fun, guys (: