Forgetting Where the Pieces Are

     As a companion to the last post, this one is about, well, forgetting where the pieces are when analyzing. Even a guy who calculated some of the most fantastic combinations ever, Mikhail Tahl, recalled how in his first serious match he rejected a line that left him a Rook ahead and instead analyzed a fantastic and beautiful tactical sequence which he finally decided to play. The problem? The whole idea was based on a move that was impossible. 
     In his 1951 match against Botvinnik, David Bronstein went into a variation he determined would win, but ended up losing the exchange and should have probably lost the game because he mentally made two moves in a row. Luckily for him, he eventually managed to draw. 
     At Hastings in 1961/62 Botvinnik spent a lot of time studying the position and then missed a win in an elementary ending when he mentally placed Gligoric's King on the wrong square.  The result was a wasted 100-plus move effort. 
     Tiger Lilov's Chess School has a brief 13 minute video titled Learn How to Calculate Successfully in which he offers some basic advice that may be helpful. 
     This game is from the fourth tournament in a series of six organized by the GMA from 1988 to 1989 as a World Cup and was held in Barcelona in the spring of 1989. This tournament was Kasparov's third consecutive victory in the World Cup. 

1-2) Kasparov and Ljubojevic 11-5 
3) Salov 10-6 
4) Korchnoi 9.5-6.5 
5-6) Huebner and Short 9-7 
7) Nikolic 8-8 
8-12) Vaganian,Yusupov, Ribli, Spassky and Beliavsky 7.5-8.5 
13) Speelman 7-9 
14-15) Hjartarson and Seirawan 6.5-9.5 
16-17) Illescas-Cordoba and Nogueiras 5.5-10.5 

     In the game presented here Iceland's GM Johann Hjartarson made a curious error on move 26. He saw the winning line but rejected it when he got three moves deep in his calculation. The reason? In his head he played an impossible move. Here is the position he visualized after making the illegal 28...cxb3 followed by 29.Qxc5 Qa5 and black has a winning position.