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4th July 2009, 05:22am
#1
by sanjayd1998
Bangalore India
Member Since: Nov 2008
Member Points: 169

White to play and mate in three.

Hint:The obvious move is e8Q (or g8Q), but Black replies 1...Bb8 and if White takes the bishop then Black is stalemated, while otherwise Black continues with 2...Ka8 and there is no mate. But now comes a typical piece of lateral thinking-if only White's queen and rook were the other way round on the eighth rank, then 1...Bb8 wouldn't be a defense. How can white achieve this?

If White promotes a pawn immediately by 1 e8Q or 1 g8Q, then Black replies 1...Bb8, and White cannot take the bishop because of stalemate, so there is no mate in two. The correct plan is to arrange for the rook to be on the other side of the queen, so that ...Bb8 is no longer an effective defense. However, 1 Rg8? (1 Rf8? is also met by 1...Bd6) fails to 1...Bd6 2 e8Q Bf8, blocking the back rank.
The rook must go to the very end, so as to give White a choice of promotions. White doesn't threaten anything, because 2 e8Q and 2 g8Q would be met by ...Bd8, but Black's bishop cannot stay on c7. After 1...Bd6 White plays 2 g8Q, intending Qa8 mate, while if the bishop moves to any other square on the b8-h2 diagonal, White forces mate by 2 e8Q. 1...Bd8. The best defense.
2 e8Q? and 2 g8Q? are met by 2...Kb8, while 2 exd8Q? is stalemate. 2  exd8B!   White avoids stalemate by underpromoting. Once again there is no threat, but Black's king is forced to move onto the dangerous back rank.   2...Kb8  3  Bxb6 mate.

4th July 2009, 12:12pm
#2
by SerFuLian
Yangshuo China
Member Since: Jun 2009
Member Points: 17

"If White promotes a pawn immediately by 1 e8Q or 1 g8Q, then Black replies 1...Bb8, and White cannot take the bishop because of stalemate, so there is no mate in two."

Ummm... Is this true? I think black is able to postpone mate to 4 moves. After black plays bb8 whites second move is to promote the other pawn and ka1 is the only move black can make without giving mate on the 3rd by moving the bishop (no stalemate). It takes 2 more moves to mate... 4 in all.

4th July 2009, 12:23pm
#3
by Tajamoen
International
Member Since: Apr 2009
Member Points: 394

This is another mate in three:

4th July 2009, 12:58pm
#4
by amiraz
Israel
Member Since: May 2008
Member Points: 270

Tajamoen, its a mate in 4 after 1.g8=Q:

5th July 2009, 02:19am
#5
by sanjayd1998
Bangalore India
Member Since: Nov 2008
Member Points: 169
Tajamoen wrote:

This is another mate in three:

 

 

After 1 g8Q Bb8 2 Qa2 Black plays 2...Bd6 and if White plays 3 Kb3+ Black simply plays 3...Ba3 delaying the mate by one move. There is only ONE mate in three.

5th July 2009, 03:18am
#6
by Lord-Chaos
Devon England
Member Since: Feb 2009
Member Points: 1961

Oh yeh, i think theres 3 ways of mating in 3 =D

5th July 2009, 03:31am
#7
by amiraz
Israel
Member Since: May 2008
Member Points: 270

Lord-Chaos, there is only 1 mate in 3 and that is 1.Rh8.

1.Rf8, Bd6 and there is no mate in 3.

1.Rg8, Bd6 and there is no mate in 3.

5th July 2009, 03:39am
#8
by sanjayd1998
Bangalore India
Member Since: Nov 2008
Member Points: 169
amiraz wrote:

Lord-Chaos, there is only 1 mate in 3 and that is 1.Rh8.

1.Rf8, Bd6 and there is no mate in 3.

1.Rg8, Bd6 and there is no mate in 3.

Yeah, you are right but tell this to Lord-Chaos.

 
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