More Sidewalk Puzzles - Page 4 - OzChess

**mrmip** · 04-22-2009, 11:51 PM

Originally Posted by Calvin

Why is it necessary to sacrifice the knight or was that just for show, to make the whole combination look better?

No. It is essential to 'box in' the black rook. Perhaps AO could do the honours and explain what happens if black responds to 1.Ng5! with 1...Rxh6 or 1...Rxh4? This may also clarify Brokenwall's astute hint.

**Just2Good** · 04-23-2009, 12:52 PM

Originally Posted by mrmip

No. It is essential to 'box in' the black rook. Perhaps AO could do the honours and explain what happens if black responds to 1.Ng5! with 1...Rxh6 or 1...Rxh4? This may also clarify Brokenwall's astute hint.

The reason the Knight move was so important was to remove influence on the g1 square, which becomes a necessary escape square that the King must be allowed to flee to in order to get the forced mate to work.

**mrmip** · 04-23-2009, 08:40 PM

OK. Here is the complete solution:
[spoiler]

1.Ng5 and now
1...Rxh6 2.b8=R Rb6 3.Rxb6 Kg1 4.Rb1#
1...Rxg5 2.c8=R Rc5 3.Rxc5 Kg1 4.Rc1#
1...Rxh4 2.d8=R Rd4 3.Rxd4 Kg1 4.Rd1#

Note that white should plan ahead which pawn to promote to a rook depending on black's first move. The pawn must be selected so that the promoted rook will capture the white rook on a square that interferes with Ba7's control of g1, releaving the stalemate. This fairly common theme is known as an 'Indian' theme.
[/spoiler]

**Just2Good** · 04-24-2009, 11:48 AM

OK. Here is the complete solution:

Thanks Mr Mip, I just assumed people knew how the other 2 variations led to easy mates.

04-22-2009, 11:51 PM	#46 (permalink)
mrmip Member Join Date: Mar 2009 Location: Kerava, Finland Posts: 64	Originally Posted by Calvin Why is it necessary to sacrifice the knight or was that just for show, to make the whole combination look better? No. It is essential to 'box in' the black rook. Perhaps AO could do the honours and explain what happens if black responds to 1.Ng5! with 1...Rxh6 or 1...Rxh4? This may also clarify Brokenwall's astute hint.

04-23-2009, 12:52 PM	#47 (permalink)
Just2Good Tin Cup Champ 2004 Join Date: Jul 2007 Location: Cairns Posts: 6,233 ICC Handle: Advantage FICS Handle: Advantage	Originally Posted by mrmip No. It is essential to 'box in' the black rook. Perhaps AO could do the honours and explain what happens if black responds to 1.Ng5! with 1...Rxh6 or 1...Rxh4? This may also clarify Brokenwall's astute hint. The reason the Knight move was so important was to remove influence on the g1 square, which becomes a necessary escape square that the King must be allowed to flee to in order to get the forced mate to work. __________________ . "The fox knows many things, but the hedgehog knows one big thing." ~ Isaiah Berlin ~

04-24-2009, 11:48 AM	#49 (permalink)
Just2Good Tin Cup Champ 2004 Join Date: Jul 2007 Location: Cairns Posts: 6,233 ICC Handle: Advantage FICS Handle: Advantage	OK. Here is the complete solution: Thanks Mr Mip, I just assumed people knew how the other 2 variations led to easy mates. __________________ . "The fox knows many things, but the hedgehog knows one big thing." ~ Isaiah Berlin ~

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04-23-2009, 08:40 PM	#48 (permalink)
mrmip Member Join Date: Mar 2009 Location: Kerava, Finland Posts: 64	OK. Here is the complete solution: [spoiler] 1.Ng5 and now 1...Rxh6 2.b8=R Rb6 3.Rxb6 Kg1 4.Rb1# 1...Rxg5 2.c8=R Rc5 3.Rxc5 Kg1 4.Rc1# 1...Rxh4 2.d8=R Rd4 3.Rxd4 Kg1 4.Rd1# Note that white should plan ahead which pawn to promote to a rook depending on black's first move. The pawn must be selected so that the promoted rook will capture the white rook on a square that interferes with Ba7's control of g1, releaving the stalemate. This fairly common theme is known as an 'Indian' theme. [/spoiler]