Sunday, June 15, 2014

Rook vs Connected Passed Pawns: Part 1

Already from our Rook vs Lone Pawn series we can already see that a single infantryman can give the rook so much headaches. Now what happens if there were two pawns? Will the rook be able to fight them all by himself, or will the pawns overwhelm the rook like the zombie apocalypse?

The problem isn't that they're strong, but that there's just too many of them

In a Rook vs Two Pawns endgame, the first thing that we need to know is that unlike the minor piece, the rook performs well when against two disconnected pawns since its long-range abilities enable it to switch from one target to another quickly. On the other hand, connected passed pawns present a major problem for the rook since the enemy king is able to protect both pawns, which in turn protect each other!

To make things simple we will only discuss connected passed pawns in this series of articles; disconnected pawns will be our main topic in subsequent articles. In the case of connected passed pawns, the result of the game is often determined by the placing of both kings. If both kings are far away from the pawns, then the pawns will win if they are able to get to the 6th rank and beyond:

Whoever to move wins

Black to move wins since his pawns can reach the 6th rank:

1... g3
2. Rh8+

Neither the rook nor king are able to stop the connected passed pawns when they are beyond the 6th rank (e.g. 2. Rg7 f2 3. Rf7 g2 4. Rxf2 g1=Q -+) so White's best chance will be to rain checks and hope for a miracle

2... Kd7

No miracles! Black simply walks his king over to the rook and the checks will eventually peter out.

3. Rh7+ Ke6
4. Rh6+ Kf5
5. Rh5+ Kg4
6. Rh7 f2
7. Rf7 g2
8. Rxf2 g1=Q
0-1

Black reaches a theoretically won Queen vs Rook endgame (you can try winning this as an extra challenge!)

White to move wins because one of the pawns has not yet crossed the 6th rank:

1. Rf7

It is important to put the rook behind the more advanced pawn; 1. Rg7? loses after 1... f2 2. Rf7 g3!

1....  Kd8

Or 1... g3 2. Rxf3 g2 3. Rg3 +-

2. Rf4 Ke7
3. Rxg4
1-0

And the win should be quite obvious to us by now.

...

In order for the rook to have better drawing chances when the enemy pawns are on the 6th rank and beyond, the pieces must be positioned in such a way that:

  1. The rook and his fellow king can deliver mating threats
  2. One of the pawns can be captured with a check

In the following position, Black's pawns are on the verge of promotion, but White saves the day by pursuing Black's king with continuous mating threats:

White to move draws


1. Rh1 Ke8

Or 1... Kg8 2. Rg1+ Kf8 returning to the original position

2. Ke6 Kd8
3. Kd6 Kc8
4. Kc6 Kb8
5. Rh8+!

Not 5. Kb6?? b1=Q+ -+

5... Ka7
6. Rh7+ Ka6
7. Rh8 Ka5

7... Ka7 is met with 8. Rh7+

8. Kc5 Ka4
9. Kc4 Ka5
1/2-1/2

A draw is inevitable, since 9... Ka3?? leads to 10. Ra8#. It is interesting to note that had the pawns been on b2 and c2 instead, White's mating threats will not materialize after 4. Kc6 and Black would win.

...

In the following study by Salvioli, White cannot win since Black's pawns have reached the 6th rank. However, White saves his half-point because the position of Black's king poses tactical problems when the pawns reach the 7th rank:

Salvioli
1887
White to move draws... again


1. Kf4 Kg2

Or 1... a2 2. Ra1 Kh3 (2... b2?? 3. Rxa2 and Black cannot play 3... b1=Q because his pawn is pinned to the king!) 3. Kf3 Kh4 4. Kf4 and Black cannot win because of the continuous mating threats

2. Rb1!

It is important to choose the correct pawn to attack; 2. Ra1? loses after 2... b2 3. Rb1 Kf2 4. Ke4 Ke2 5. Kd4 Kd2 6. Kc4 Kc2 and the Black king chases the helpless rook away.

2... a2

2... b2 is met by 3. Ke3 and if Black plays 3... a2?? White wins after  4. Rxb2+. This shows the problems encountered when the king is on the same rank as his pawns: The enemy rook can capture the pawns with a check!

3. Ra1 Kf2
4. Ke4 Ke2
5. Kd4 Kd2
6. Kc4 Kc2

Or once again 6... b2 7. Rxa2 Kc2 and Black cannot promote the pawn because of the pin.

7. Kb4 Kb2
8. Rh1 a1=Q
9. Rxa1 Kxa1
10. Kxb3
1/2-1/2

A fine illustration of the theme of winning a pawn with check.

...

To wrap up Part 1, we have seen how the pawns work together to overpower the rook once they have crossed the 6th rank, with neither king having any ability to interfere. Once this happens, the rook can only save a draw if he is able to deliver mating threats, or is able to win a pawn with check. In Part 2, we will look at what happens when both kings are closer to the action.

Links:
Rook vs Lone Pawn Part 1: http://nushsblackknights.blogspot.com/2014/05/rook-vs-lone-pawn-part-1.html
Rook vs Lone Pawn Part 2: http://nushsblackknights.blogspot.com/2014/05/rook-vs-lone-pawn-part-2.html
Rook vs Lone Pawn Part 3: http://nushsblackknights.blogspot.com/2014/05/rook-vs-lone-pawn-part-3.html
Rook vs Lone Pawn Part 4: http://nushsblackknights.blogspot.com/2014/06/rook-vs-lone-pawn-part-4.html

Sources:
"Rosen's Chess Endgame Training" by Bernd Rosen
"A Guide to Chess Endings" by Max Euwe
http://compactiongames.about.com/od/screenshots/ig/Left-4-Dead-2-Screenshots/Left-4-Dead-2-Screenshot-.-eQg.htm

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