Wednesday, November 24, 2010

Some Endgame Lessons

Prospect split with the Groves last week, losing a tough match to undefeated Buffalo Grove 42.5-25.5 on Tuesday and beating Elk Grove on Thursday 56.5-11.5. With some better endgame play, the Buffalo Grove match could have been much closer.

Endgame Lesson #1: King and Rook v. King and Pawn

The following position (more or less) occurred on 4th Board with Nick Martin playing white against Buffalo Grove's Matt Wiewel.

This should be a fairly easy win for White. Black will be compelled to give up his for White's d-pawn and White's king and rook should be able to round up the remaining Black pawns easily. However, it is possible to go wrong, so it is worthwhile considering an even more basic position.

The only way for White to win here is with 1.Rb5 cutting off the Black king from supporting the pawn. 1...f3 2.Rb3 f2 3.Rf3 f1=Q 4.Rxf1 and hopefully White knows how to mate with a king and rook. It is vital that White cut off the Black king immediately because the game is drawn if Black's king and pawn are another square farther down the board.

Now 1.Rb4 doesn't do the trick. After 1...f2, White is forced to play 2.Rb1 Kb4 3. Rf1 Kb3 and the game is drawn because White will be forced to trade his rook for the Black pawn.

Returning to the position from Martin-Wiewel, the easiest way for White to avoid a position where his rook might have trouble coping with the Black king and pawns is to get the White king into the action. Unfortunately, White tried to win the game without his king. 1.Ke8?! Heading the wrong direction. After 1.Ke6 Ra8 2.d8=Q Rxd8 3.Rxd8, the White king would have been two squares closer to the action than it was in the game after 1...Ra8+ 2.d8=Q Rxd8+ 3. Kxd8 Kf6. Still if White gets his king moving the win should be fairly easy. 4.Rf2?! Still on the wrong track. 4...Kf5 5.h3??. This was White's last chance, he still could have won with 5.Ke7 g4 6. Kd6 f3 7.Kd5 Kf4 8. Kd4 g3 9.hxg3+ Kxg3 10.Kf3. Now the win is no longer there after 5...g4 6.hxg4 Kxg4

The White king is too far away. The rook is a wonderfully powerful piece, but it cannot handle the combined king and pawn by itself. If it cannot cut off the king before the pawn has advanced too far, the rook must have the king's help to cope.

Endgame Lesson #2: Defending Rook and Pawns v. Rook and Pawns.

There is an old aphorism in chess that goes "All rook endings are drawn." This is obviously not true, but rook endings often offer unexpected drawing possibilities. Before considering the ending that arose between Michael Monsen and Matt Wiewel on 5th Board in the Buffalo Grove match, let's start with another basic position.

This position is drawn as long as White toggles his king between g2 and h2 because the Black rook is stuck in front of its own pawn. If White plays 1.Kg3, Black wins with 1...Rg1+ 2.Kf2 a1=Q. If White plays 1.Kf2, Black wins with 1...Rh2 2.Rxa2 Rh2+ 3.Kg3 Rxa2. However, after 1.Kh2, the Black rook cannot escape without dropping the pawn. If Black tries to bring his king over to help, the White rook will check it away.

Black has an extra pawn, but as in the previous diagram, his rook is defending the pawn from in front and the Black king is in no position to relieve the rook of its defensive chores. White panicked with 43.Rd3?? and was helpless against Black's extra pawn after the exchange of rooks . However, if White could have gotten his rook behind Black's passed pawn, I think he should have had pretty good drawing chances. 43. Rd5! looks very solid. After 45...a4 Ra5, it is hard to see how Black is going to improve his position as his king is tied to the defense of the f-pawn and the rook is tied to the a-pawn. If Black should try to bring his king over to support the a-pawn, White can bring his king over to defend and leave the rook to defend pawns on the other side.

Wednesday, November 10, 2010

The Queen and Pawn Ending

Which player has the better chances in the following position?

While having an extra pawn is usually preferable, when the only pieces on the board are the queens, a single pawn that is far advanced can be worth more than several pawns that are not if the advanced pawn cannot be blockaded by the opponent's king. In Patel v. Monsen, the players agreed to a draw after 44...Qg7 45.Qf4+. While a draw was not an unreasonable result, had the match still been in doubt, it would have been reasonable for Black to have played for a win.

The problem for White is that the only way to stop the Black pawn from advancing is by keeping the Black king in check. As a result, he does not have the time he needs to advance his own pawns. The problem for Black is that his king is in the of a wide open board and White has lots and lots of checking opportunities. Nevertheless, White has to careful not to deliver a check that can be blocked with a counter-check or with a pin that will force the exchange of queens. For example, after 44...Ke7, 45.Qe4+ would be met with 45...Qe6 forcing the queens of the board. Black may be able to use this possibility to leave White without a good check for a move or two which is all Black needs to advance the pawn.

One possibility after 44...Ke7 is 45.Qg5+ Qf6 46.Qc5+ Qd6 47.Qg5+ Kf7 48.Qf5+ Qf6 49. Qh7+ Qf8.
White now has no checks and he must try to prevent the pawn from advancing with 50. Qb1. Black then can prepare the advance with 50...Qf7 when Black can force the queens off the board after either 51.Qc8+ Qe8+ or 51. Qc5+ Qe7+. After 51.Kd2 a2 52.Qa1 Qf2+ 53.Kd3 Qxh2, Black has reestablished material equality, but he is going to be subjected to another avalanche of checks. Whether Black can actually force the pawn home is far from clear, nevertheless, there will be plenty of chances for White to go wrong and the winning chances definitely lie with Black.

Two things to remember in endings with queens and pawns on both sides:

(1) Having the most pawns is not as important as having the most advanced pawn.

(2) Even though the board looks wide open, don't assume that perpetual check is inevitable. It is often possible to leave your opponent without any good checks.

Prospect moves to 4-1

Losing 49-19, Prospect discovered last week that even with the graduation of expert Zach Kasiurak, Barrington is not a team to be taken lightly. However, it rebounded yesterday with a 53-15 win over Conant. Next week brings the groves of the buffalo and elk.