notyetagm: White to move: 28 ?
 click for larger view28 f5-g5!
 click for larger viewNow I understand this particular <TREBLING> idea. The point is that in the first diagram, the g7-square is one of the most dangerous things on the chessboard: the dreaded <LOOSE SQUARE NEXT TO THE KING>. The White g1-rook attacks the g7-square, while the Black h8-king defends the g7-square. <<<It is important to note that the presence of the White g7-rook -on- the g7-square is irrelevant to the <LOOSENESS> of this square!>>> The g7-square has one attacker (White g1-rook) versus one defender (Black h8-king), no matter what piece is on the g7-square or if there is no piece on this square. Then with 28 f5-g5!, White (Kramnik) simply brings his White f5-queen into contact with this <LOOSE SQUARE NEXT TO THE ENEMY KING>. So now the g7-square is <EN PRISE>, with -two- attackers (White g1-rook, g5-queen) versus only -one- defender (Black h8-king). <<<Again note how the White g7-rook is ignored when counting how many pieces attack and defend the g7-square.>>> Now the -only- thing that prevents White from playing 29 g5-g7# is the presence of the White g7-rook (<SELF-BLOCK>). So in the final diagram, White is threatening to vacate this square with tempo (<CLEARANCE>) via 29 g7xh7+! and then playing 30 g5-g7#. Hence Black defends the g7-square with 28 d8-d7. |