Friday, December 20, 2013

Revising Basic Rook Endgames; Part 3

In the last section of our revision we shall take a look at how a rook can active or passive in a given position, and the consequences.

The long-ranging capabilities of the rooks enable them to serve multiple roles throughout the course of a game. They protect the king in a castled position, seize open files, and help to support the advance of passed pawns. From our our revision in Part 2, we can also see that they have the ability to cut off entire files to prevent the advance of enemy infantry.

However, rooks also have their own weaknesses. When blocked by enemy or friendly pieces their long-range powers become limited, and they instead become targets for attack. If not placed in a proper position they can actually become passive pieces, tied down to the defence of weak spots and succumbing to the powers of more active enemy pieces. Hence the terms active and passive rooks come about, and they are an important factor which often decides which direction the endgame swings.


Active and Passive Rooks

From Part 2 we saw how putting a rook behind a passed pawn is effective in helping/stopping its advance, as compared to a rook in front which gets in the way. In fact, this is a special case of active vs passive rooks-- the rook behind the pawn is usually more active since it has more freedom to move about and yet watch over the pawn at the same time.

To have a better understanding of the terms active and passive, let's take a look at the following position:

White's rook is active, while Black's is passive

A quick glance can see that White's rook is better off than Black's. White's rook is attacking the pawn on a7, and can roam around the 7th rank or switch to attack another target if he wishes to. On the other hand, his Black counterpart is tied down to the defense of the a7 pawn, and cannot move anywhere else as long as White continues attacking a7. To put it in another form, White has the "dominant", or active rook, while Black has the "slave", or the passive rook.

(And over here, Tarrsch's rule of putting the rook behind the pawn definitely does not apply!)

While this may seem trivial in the simple position shown above, the concept of active and passive rooks can be externally useful when it comes to more complex positions like this:

White to move

Black is a pawn up, but White simple seizes the advantage with the move:

1. Rd7!

After which it is quite clear that White's rook is more active than Black's: He attacks the a7 pawn and ties down the enemy rook to its defense. White's plan will be to use his active rook to pin down the enemy king and rook, while his own king moves in and helps pick off the Black pawns.

1... Kf8
2. Rb7 Ke8
3. Kc3

Not falling for 3. Kd3? Rd8+ 4. Ke4 Rd7 5. Ke5 Ke7

3... Kf8
4. Kd3 Rd8+

After 4... Ke8 5. Ke4 Kf8 6. Kd5 Rd8+ 7. Kc6 Rc8+ 8. Kd7 Ra8 9. Rc7 the White king will enter via Kc6-Kb7 and Black's pawns will fall one-by-one

5. Ke4 Rd4+

Black manages to activate his rook but the White king has already forced his way into Black's pawn mass.

5... Re8+ 6. Kd5 Re7 (6... Rd8+ 7. Kc6 Rc8+ 8. Kd7 Ra8 9. Rc7) 7. Kd6 Re6+ 8. Kc7 Re7+ 9. Kb8 also wins for White

6. Ke5 Rxc4
7. Rxa7 Rxh4
8. Rd7!

Another alternative, but not-so-strong variation for White is 8. Rb7 Ra4 9. Rxb6 h4

8... Ra4
9. a7 Kg7 (D)


9... Ke8 loses even faster-- after 10. Rb7 h4 11. Rb8 +-

Despite being two pawns down, White is winning here because 1. His passed pawn is further ahead compared to Black's 2. His king is in the action while Black's is sitting on the sidelines and 3. Black's rook is tied down to guarding the a file to prevent White's pawn from promoting. White now wins by walking his king over to the b file and escort the pawn to promotion, while his rook leaps to the first rank to stop Black's passed pawn. The resulting variations I will show in the KnightVision viewer:


Throughout the study we see how White's active rook ties down Black's passive counterpart by attacking vital squares, thus allowing the White king to enter and escort the pawn to promotion. This is just one of the many examples of the dominance of active rook over passive ones.


...

The activity of a rook is also decided by its ability to quickly respond to new and emerging threats across various parts of the battlefield. Rooks are most lethal when they are mobile; a rook that is blocked by friendly/enemy pieces cannot maneuver quickly across the board and is therefore passive, akin to a piece of armour bogged down in the mud.

Hey but it's still an excellent pillbox, though the most expensive one in the world!

The difference between a rook that can move about freely and one that cannot may be enough to make a difference, as we can see in the next example:

White to move and pick up the point

Looks...a little like the Philidor Position right? But it isn't, because it is White to move here and White can win! Black's rook is bogged down-- it cannot leave the 1st rank because of the threat of 1. Rh8#. White wins easily by swinging his more active rook over to the other side of the board:

1. Ra7!

And the threat of 2. Ra8# forces Black to continue 1... Ke8 2. Ra8+ (2. d7+ Ke7 3. Kc7 also wins) Kf7 3. Rxg8 where after 3... Kxg8 the resulting pawn endgame is a no-brainer win for White.

Remember how we talked about the "swing the rook to the other side of the board" trick in Part 1? Now you see it again here, and that's one of the reason why active rooks often dominate over passive ones!

And with that I close off our revision on basic rook endgames. By now most of these should be trivial to y'all, but do spend some time going through them again. What we have gone through-- Lucena and Philidor Positions, active and passive rooks, and other basic stuff-- will serve as important building blocks in our study of more complex rook endgames in the future.

Links:
Part 1: http://nushsblackknights.blogspot.sg/2013/12/revising-basic-rook-endgames-part-1.html
Part 2: http://nushsblackknights.blogspot.sg/2013/12/revising-basic-rook-endgames-part-2.html

Sources:
"Silman's Complete Endgame Course" by Jeremy Silman
http://www.strangevehicles.com/content/item/120829.html

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