[blind-chess] Chess Article #55: The rook and Pawn Versus Rook endgame (Part 2)
- From: Roderick Macdonald <rmacd@xxxxxxxx>
- To: Blind Chess Mailing List <blind-chess@xxxxxxxxxxxxx>
- Date: Thu, 17 Jun 2010 20:38:19 -1000 (HST)
Chess Article #55:
The Rook and pawn versus rook endgame
Adapted and Condensed from
Wikipedia, the Free Encyclopedia
Part Two of Three Parts
++4. Defensive methods
Often White will not be able to utilize one of the winning methods.
Black has several defensive methods available, depending mainly on
the position of the pawn and his king.
If the defending king is in front of the pawn and the attacking
king and pawn have not yet reached their sixth rank, the Philidor
position (or Philidor defense) easily works to secure a draw. If
the defending king can not get in front of the pawn but is not cut
off, the short side defense can be used. If the pawn is a rook pawn
or knight pawn, the back rank defense can be used. The back rank
defense can also be used when the pawn is on other files if the
attacking king has not reached the sixth rank. If the king is cut
off along a file, the frontal defense may work, depending on the
file of the pawn and how far advanced it is.
(See Chess Article #51 for more on the Lucena Position)
++4.a Philidor position
Diagram #10:
Philidor position
White: King at f5, Rook at h7, Pawn at e4
Black: King at e8, Rook at b6
Philidor's position, or third rank defense. Black is defending the
Philidor position, and draws, even if White is to move.
Philidor's position (see diagram #10) illustrates an important
drawing technique in this endgame. The technique is also known as
the third rank defense and works when the defending king is in
front of the pawn and the attacking king and pawn have not reached
their sixth rank. Black keeps his rook on his third rank to keep
the white king from reaching that rank. If White advances the pawn
to its sixth rank (Black's third rank), then the king is deprived
of shelter, so Black moves his rook to the eight (or seventh) rank,
and keeps checking the white king from behind. It is very important
that the defender keep his rook on his third rank, and move to the
far side of the board only after the attacking pawn has moved to
its sixth rank. (An exchange of rooks will result in a drawn
position, see king and pawn versus king endgame.) See Philidor
position for more details (Fine & Benko 2003:294).
There are three errors that Black must avoid:
1. Immobilizing the rook
2. Allowing the king to be driven away from the queening square
3. Playing the king to the wrong side
Philidor's defense can also be used with the black rook on the
fourth rank, if White's king and pawn have not reached that rank.
If this defense is used, the black king should be on the second
rank. The principle is the same: Black keeps his rook on the fourth
rank, keeping the white king from advancing to that rank. If the
pawn advances to that rank, Black moves the rook to the eighth rank
and checks the king from behind.
(See also Chess Article #52 for more ont he Philidor Position.)
++4.b Back-rank defense
Diagram #11:
White: King at f6, Rook at a7, Pawn at g6
Black: King at g8, Rook at b8
Back rank defense. Black draws using the back-rank defense.
The back-rank defense always works if the pawn is a rook pawn or
knight pawn and the defending king is in front of the pawn. The
defending king blocks the pawn and the rook is on the first rank
preventing checks by the rook. In diagram #11, Black draws. If 1.
g7 then 1. ... Rb6+ draws and if 1. Rg7+ then 1. ... Kh8 draws.
White's best attempt is:
1. Kg5 Rc8
(waiting passively, also known as the passive defense)
2. Kh6 Rb8
3. Rg7+
(the only trick for White)
3. ... Kh8!
If 3. ... Kf8? then 4. Kh7 Rb1 5. Rf7+ Ke8 6. Rf4 and White gets to
the Lucena position.
4. Rh7+ Kg8
5. Ra7 Rc8
and White makes no progress. The defense fails for other pawns (if
the attacking king has reached the sixth rank) because White has
another file available to go around the pawn (Emms 2008:20).
Diagram #12:
Averbakh and Kopayev
White: King at g5, Rook at a7, Pawn at f6
Black: King at f8, Rook at b8
White to move wins. Black to move draws
If the attacking king has not reached the sixth rank, the defense
works for any pawn. In the second diagram (#12), White to move wins
by getting his king to the sixth rank so the defending rook can not
leave the back rank because of the threat of checkmate. This
illustrates how the defense fails for a bishop pawn or central
pawn:
1. Kg6 Rd8
2. Rh7 Kg8
3. f7+ Kf8
4. Rh8+ Ke7
5. Rxd8 and wins.
If Black is to move in diagram #12, he draws:
1. ... Rb1!
which neutralizes the threat of Kg6, because Black check from
behind and there is no immediate threat of checkmate by White
(Averbakh & Kopayev 1987:115). Black checks from behind, as in the
Philidor defense.
If neither the pawn or king have reached the sixth rank, Black can
normally draw by reaching the Philidor position, above.
++4.c Defending king is in front of pawn, but pawn is too
advanced for the Philidor position
Diagram #13:
White: King at g1, Rook at a1
Black: King at g3, Rook at b2, Pawn at f3
Can not reach Philidor position. White to move can not reach the
Philidor position, and loses.
Diagram #14:
White: King at g1, Rook at a1
Black: King at h3, Rook at b2, Pawn at g3
Knight's pawn. Similar position with knight's pawn, but White
draws.
Sometimes the defender's king is in front of the pawn, but the rook
can not get to its third rank to reach the Philidor position. Thus
he has two choices: try to attack from behind, or retreat to the
back rank with his rook to guard the mating threats. The diagrams
show such back-rank positions.
For a bishop pawn (see diagram #13) or central pawn, if the
defending rook is tied down to the back rank, he loses:
1. ... Rg2+
2 Kf1
(or Kh1)
2. ... Rh2!
3 Kg1 f2+
4. Kf1 Rh1+
winning the rook
But the defender can hold the draw with an accurately-conducted
"active defense" from behind the pawn while it is still on the
fifth rank, with the king moving to the short side (see next
section).
But with a knight pawn (see diagram #14), the attacker has no file
equivalent to 2. ... Rh2, so he can not make progress. Here, the
defender should avoid the active defense (attacking the pawn from
behind while it is on the fifth with the rook) fails, because his
king will be forced to the long side (stepping the other way would
lose immediately because of the corner, allowing immediate mate).
The defender can draw against the rook pawn either way, because
most king and pawn versus king positions are drawn with the rook's
pawn (see King and pawn versus king endgame - Rook pawn), (Mednis
1982:15-19), (Dvoretsky 2006:144), (Ward 2004:37-42).
++4.d "Short side" defense
Not all positions similar to the Lucena position above are wins for
the superior side -- it depends on the position of Black's rook and
king (relative to White's pawn), and which side is to move. In
positions such as the position in this diagram #15, the defending
rook must be at least four files away from the pawn on the "long
side" for the defense to work (the "checking distance"); otherwise
the white king can support its pawn and approach the black rook to
drive it away. The black king needs to be on the "short side" so it
will not block checks by its own rook. This method was worked out
by Josef Kling and Bernhard Horwitz (de la Villa 2008:129-32).
Diagram #15:
White: King at e8, Rook at f1, Pawn at e7
Black: King at g7, rook at a2
Siegbert Tarrasch, 1906
The short side defense. Black to play draws. (White to move wins.)
As an example, Black to move draws in this diagram #15. The reason
is that Black can check the white king from the side with his rook,
and the rook is just far enough away from the white king that if it
tries to approach the rook to stop the checks, the rook can get
behind the pawn and win it, resulting in a drawn position. For
example:
1. ... Ra8+
2. Kd7 Ra7+
3. Kd6 Ra6+
4. Kd5 Ra5+
5. Kc6 Ra6+
(if 5 ... Ra8 6. Ra1! (either black takes the rook and the white
pawn queens, or it forces the enemy rook off the vital a-file that
has "checking distance", the rook moves on the back rank, followed
by 7. Kd7, and the pawn promotes)
6. Kb7 Re6
with a draw after winning the pawn, which can no longer be defended
by its king (Emms 2008:21-23).
Tarrasch, 1906
Diagram #16:
White: King at d8, Rook at e1, Pawn at d7
Black: King at f7, rook at a2
White wins
If White's king and pawn are moved to the left, White wins as in
the Lucena position above. With a few exceptions, the defending
rook must be at least four files over from the pawn for this
defense to work (which is why the defending king should go to the
short side, to not block checks by his rook).
1. ... Ra8+
(1. ... Rc2 leads to a Lucena position)
2. Kc7 Ra7+
3. Kc8 Ra8+
4. Kb7 Rd8
5. Kc7!
and White wins (Emms 2008:21-23). The rook was too close to the
pawn, so White's king could both approach the rook to prevent
checks and return to protect the pawn.
++4.d1 Short side defense, less advanced pawn
Diagram #17:
White: King at g5, Rook at a7, Pawn at f5
Black: King at f8, rook at b1
Short side defense, less advanced pawn.
Black to move should play Rb6 with an easy Philidor draw. But White
to play can prevent that, and Black must be careful.
1. Kg6
(This threatens 2. Ra8+ Ke7 3. f6+ driving the black king far from
the pawn. See the Lucena Position next section for White's winning
method.)
1. ... Rb6+
This is too late because of 2. f6, forcing Black to retreat to the
back rank, which is a loss as shown in the previous section. The
point of Philidor's third rank defense is to prevent White from
moving the king to the sixth rank before the pawn.
2. Kf6
Diagram #18:
White: King at f6, Rook at a7, Pawn at f5
Black: King at f8, rook at f1
Position after 2. Kf6.
Black (to move) is at a crossroads: he must move his king to the
side to avoid mate, but which square?
Black's defense is:
2. ... Rf1
(Tarrasch rule, rook behind pawn)
3. Kf6
(diagram #18) (3. Ra8+ Ke7 and now the black rook stops 3. f6+)
3. ... Kg8!
(going to the short side is vital, as will become clear)
4. Ra8+ Kh7
5. Rf8
Other moves make no progress because of Black's obeying the
Tarrasch rule. E.g. 4. Ke6 Kg7 and 5. f6+ is impossible. The main
move protects the pawn and threatens 5. Ke7 followed by f6)
5. ... Ra1!
(now Black threatens to check from the side to keep White from
making any progress. He needs space to do this, which is why the
king must move out of the way to the short side. There must be at
least three files between Black's rook and the pawn, otherwise
White's king can protect his pawn while attacking Black's rook and
gain time necessary to advance the pawn.
6. Re8
(one try, to use the rook to block the checks from the side)
6. ... Rf1!
Black moves behind the pawn again, so 7. Ke6 is answered by 7. ...
Kg7, as per note to move 5 (Emms 2008:22).
++4.d2 Long side blunder
If the black king went to the long side, Black would not have the
resource of checking from the side. For example, from diagram #18
above, where 3. ... Kg8! draws as shown above:
3. ... Ke8?
4. Ra8+ Kd7
5. Rf8! Rh1
6. Kg7 Ke7
(there is no room to check on the side. If 6. ... Rg1+ then 7. Kf7
followed by f6.
7. f6+
(the point of 5. Rf8)
7. ... Kd7
(7. ... Ke6 8. Re8+ Kd7 9. Re2 and converts to Lucena position,
next section)
8. Kf7
followed by Ra8 then Ra2-d2+ (or any other safe check on the d-
file).
After this, and the same if Black prevents the check by placing his
own rook on the d-file, White plays Kg7 Rg(any)+; Kf8 then f7,
reaching the Lucena position.
If the pawn is a central pawn, going to the long side with the
defending king will sometimes give the rook just enough checking
distance if it is on the rook file on the opposite side of the pawn
(Ward 2004:42). Defending this way is a far more arduous task, so
moving the defending king to the short side is always recommended
(Emms 2008:2). With the defending rook three files over from the
pawn, the attacker usually wins, but there are exceptions,
depending on the location of the attacking rook (Seirawan 2003:79).
++4.e Last-rank defense
Diagram #19:
White: King at d7, Rook at a7, Pawn at e7
Black: King at f7, Rook at b8
The last-rank defense. Black draws.
In diagram #19, Black draws:
1. ... Re8!
2. Kd6 Rb8!
if 2. ... Rg8 then 3. Ra1!. If 2. ... Kf6 then 3. Ra1! Rb8 4. Rf1+
Kg7 5. Kc6 Ra8 6. Ra1, a winning position
3. Kd7 Re8
and White can not make any progress (Emms 2008:24-25).
++4.f Frontal defense
Diagram #20:
White: King at g3, Rook at f2, Pawn at G4
Black: King at e7, Rook at b8
Frontal defense. If White is to move, Black draws using the frontal
defense. Black to move has an alternate drawing defense.
The Frontal Defense is a way that Black may keep White from getting
to the Lucena position, even if the defending king is cut off from
the pawn's file. Black's rook is well-placed on its first rank and
can check the white king or offer itself for exchange when the
resulting king and pawn versus king endgame is a draw. The farther
back the pawn is, the more likely the defense is to be successful.
To have good drawing chances, there should be at least three ranks
between the pawn and the defending rook (called the rule of three).
The file of the pawn matters too: a bishop pawn gives the best
winning chances, followed by a central pawn, followed by a knight
pawn, with a rook pawn having little chance of winning (Mednis
1998:40).
If White is to move in diagram #20, Black draws by using the
frontal defense: 1. Kh4 Rh8+! 2. Kg5 Rg8+ 3. Kh5 Rh8+ 4. Kg6 Rg8+
5. Kh5 Rh8+ and White can not make any progress (Emms 2008:18-20).
If Black to move in this position (Diagram #20), he has an
alternative drawing method that requires knowledge of the king and
pawn versus king endgame: 1. ... Rf8 to bring the king over to the
pawn. If 2. Rxf8 Kxf8 3. Kf4 Kg8! (avoids losing the opposition. 3.
Kh4 is met the same way) 4. Kf5 Kf7 or 4. Kg5 Kg7, and the position
is a draw.
diagram #21:
White: King at f3, Rook at e2, Pawn at f4
Black: King at d7, Rook at b8
Emms
White to move wins, Black to move draws. Draw if the black king is
on d6.
The frontal defense may or may not work for bishop pawns and
central pawns, even if there are three ranks between the pawn and
the defending rook. In diagram #21 from Emms, White to move wins:
1. Kg4! Rg8+
2. Kh5 Rf8
3. Kg5 Rg8+
4. Kh6 Rf8
5. Re4! Kd6
6. Kg7 Rf5
7. Kg6 Rf8
8. f5
and White will reach the Lucena position.
Black to move in that position draws, by reaching a drawn king and
pawn versus king endgame position:
1. ... Re8
2. Rxe8 Kxe8
3. Ke4 Kf8
4. Ke5 Ke7
Black to move in that position (Diagram #21) also draws with 1. ...
Kd6, getting the king to a favorable position (Emms 2008:18-20).
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