Saturday, May 17, 2014

Rook vs Lone Pawn: Part 1

The very interesting thing about pawns is how much we tend to underestimate their power. True, the pawn starts off as a lowly private which gets into the way of the long-range pieces in the opening. Yet the further he plods down the battlefield, the more his presence on the board screams for attention, and many a brutal skirmish has been fought around a single (passed) pawn in the centre. And upon reaching the 7th rank, the infantryman has already gained so much attention that he can even tie down a mighty Queen to prevent his promotion (like what happens over here: http://nushsblackknights.blogspot.sg/2014/01/queen-vs-7th-rank-pawn.html)

"Alright boys, when the bugle sounds I want y'all to charge as though there's Heineken on the 8th rank."

But then since we're learning rook endgames over here, then why am I suddenly talking about pawns? Surely the rook is powerful enough to stop a lowly pawn in its tracks?

So let's say in a case of a rook versus a lone pawn in the endgame, you might think that the result will be a dead win for the mighty rook. If that is the case, perhaps you might be surprised to know that sometimes, the pawn is able to outsmart the rook and turn a losing position into a draw. Talk about David vs Goliath!

This needs a caption, like really

If you're not convinced, take a look at the following position:

Draw

Here, White cannot win because of the following reasons

  1. His king is too far away from the enemy pawn.
  2. Black's pawn is too far advanced to be stopped by the rook alone.
  3. Black's king is close enough to support the pawn's advance.


So let's say we gave White the move here. He has two variations to choose from, but both still lead to a draw:

Variation 1:

1. Rb8

Following Tarrasch's Rule of putting the rook behind the passed pawn. But Black simply marches his pawn forwards and supports it with his king.

1... Kc4
2. Rc8+ Kd3

Hiding from the checks with 2... Kb3?! 3. Kf6 is not advisable (though Black can still draw here) since it allows White's king to step closer to the action, which is not what Black wants.

3. Kf6

Since White wants a win here, repeated checks with his rook will not help him (Black can simply shuffle his king along the c and d files if that happens).

3... b3
4. Rd8+ Kc3
5. Ke5 b2
1/2-1/2

And the only way for White to avoid a embarassing Queen vs Rook endgame will be to draw with 6. Rb8 b8=Q 7. Rxb8 Kxb8


Variation 2

1. Rh4

White tries an interesting trick over here

1... b3
2. Rh3 Kb4

It is important to keep the pawn supported! The rash 2... b2?? loses immediately to 3. Rb3!

3. Rh1

Or 3. Kf6 b2 similar to our main line.

3... b2
4. Kf6 Ka3
5. Ke5 Ka2
1/2-1/2

And once again the queening of the pawn followed by an exchange is inevitable.

...

So it seems that in order for the weaker side to force a draw in this position, there are 3 conditions which have to be fulfilled, which I have already mentioned earlier on:

  1. The weaker side's king must be close enough to support the pawn
  2. The pawn must be well advanced (usually 4th rank and beyond)
  3. The stronger side's king must not be close to the main action

Now let's see what happens if any one of these 3 conditions are not met:


Condition 1

To break Condition 1 (the weaker side's king being close enough) we will shift the Black king back by 1 file:

White to move wins, Black to move draws

Now if it were Black to move he draws by playing 1... Kc5, reaching our first position. But if it were White to move, the Black king is now too far away from the pawn to provide effective support, and White wins by an interesting trick:

1. Rh5!

Cutting off the Black king from his pawn.

1...b3

Any other king move and White will just walk his king towards the pawn, e.g. Kg6 followed by Rf5 (allowing the King to step behind the Rook so as to keep the Black king cut off) and Kg6.

2. Rh3!
1-0

The point! Now the Black king is too far away to support the hapless pawn, and 2... b2 falls to 3. Rb3


Condition 2

To break Condition 2 let us now move both the Black king and pawn back by 1 rank:

White to move wins, Black to move draws

Now, White has better winning chances because his king is closer to the pawn. Let's see what happens if White has the move:

1. Rh5 Kb6

1... b4 brings us to the 2nd position we analyzed earlier, which is a win for White

2. Kf6 Ka5

Black does some fancy maneuvering to try and advance his pawn without interference from the enemy rook. But now, the White king is close enough to catch the pawn!

3. Ke5 b4
4. Kd4+ Ka4
5. Kd3 b3
6. Kc3 Ka3
7. Rh2
1-0

And both White king and rook arrive in time to stop the pawn.

...

Now what if it were Black to move instead? Now it gets rather interesting, for the White king is close enough to cause Black some problems. Black draws by employing the tactic of direct opposition to prevent White's king from touching the pawn:


1... Kd5!

Preparing the opposition. On the other hand, the more intuitive 1... Kc5? allows the White king to infiltrate after 2. Kf6 b4 3. Ke5 b3 4. Rc8+! (forcing Black's king to step back) 4... Kb4 5. Kd4 Ka3 6. Kc3 Ka5 (6... b2? 7. Ra8#) 7. Rb8 1-0

2. Kf6 b4
3. Kf5 b3
4. Rd8+ Kc4
5. Ke4

The White king is not allowed to pass Black's defenses!

5... b2
1/2-1/2


Condition 3

Admittedly the earlier position already showed us how White has better winning chances when his king is closer to the pawn (once the pawn was shifted back), but let us ram that point home with another example:

White wins

Now White can win because his king is close enough to catch the pawn. A team effort between king and rook is necessary in this situation.

If it were White to move, things get easy after 1. Ke3 (the White king can catch the pawn in time because it is in the "square of the pawn") 1... Kc4 2. Kd2 outflanking the Black king, with 3. Rb8 to follow.

If it were Black to move, then White still wins after: 1... Kd4 (attempting to stop White's king from reaching the pawn) 2. Rh3! Kc4 3. Rh1 Kd4 4. Rb1 Kc3 5. Ke3 b3 6. Rc1+! (NOT 6. Ke2?? Kc2 with a draw) 6... Kb2 7. Kd2 Ka3 8. Rb1 Ka2 9. Kc1 1-0 with both king and rook arriving to stop the pawn in its tracks.

...


So once again here are the 3 conditions in order for the lone pawn to be able to outsmart the rook:

  1. The weaker side's king must be close enough to support the pawn
  2. The pawn must be well advanced (usually 4th rank and beyond)
  3. The stronger side's king must not be close to the main action

And we have see how breaking any of these 3 conditions will lead to better winning chances for the stronger side. But of course, one must remember not to take these 3 as absolute rules; as always, there will be exceptions and interesting deviations, of which we will take a deeper look into for Part 2.

Sources:
http://www.koreatimes.co.kr/www/news/nation/2010/01/113_58792.html
http://www.blogging4jobs.com/social-media/david-vs-goliath-someones-hijacking-my-twitter-stream/
"Silman's Complete Endgame Course" by Jeremy Silman
"Chess Endgame Training" by Bernd Rosen

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