This checkmate came from Réti-Tartakower, Vienna 1910, and involves White dropping an early checkmate on Black's uncastled King at c7 by White's Queen Bishop at d7 defended and protected by White's Queen Rook at d1 (resulting from castling to Queenside). White's Rook at d1 also takes away an escape square at d7 for Black's King. The mating pattern develops by Black making a bad move followed by a blunder (7...Qxe5? and 8...Nxe4??), allowing White to employ a brillant Queen sacrifice to force Black's King to d8, dropping a mating net on uncastled Black's King. If Tartakower had played more prosaically to counter the developing center threat, then 7...Qxe5 would not have been a bad move. In fact, analysis would yield that it is the only logical move by Black at this point having brought Black's Queen out in the checking move 6...Qa5+. Therefore, the blunder on the eighth move shows that Tartakower failed to consider the consequences of a Queenside castle by Réti and did not move to counter the center attack Réti was developing. In doing so, Tartakower turned 7...Qxe5 into a bad move because he did not know or failed for some reason to follow-up 7...Qxe5 to counter the developing center attack, allowing Réti to develop what became a now classic mating pattern known as Réti's Mate. This shows that even playing a correct move can be bad if the player does not have the chess vision necessary to followup the line of play which he or she has developed. The mating net after 9...Kxd8 10.Bg5++ (a double discovered check!) gives either Réti's Mate [10...Kc7 11.Bd8#] or Morphy's famous Opera Mate pattern (covered in the Tactics & Strategy section) [10...Ke8 11.Rd8#]. This is an example of the awesome power of a double check...a discovered check combined with the moving piece also attacking and checking the opposing King to doubly attack him...perhaps the most devastating tactical move on the board.
