According to GM Yasser Seirawan the move is played to stop the b8 knight from moving, the text move is 14.Be2 however 14.Bb5 is perfectly good and tempts black to play a6 which is a slight innacuracy. Spassky should have played Qb7.
For more info see
http://home.wi.rr.com/etzel/72game6.htm
This game is Fischer vs Spassky from the 1972 World Championship. In this game Fischer won.
I am trying to understand certain moves and why they were made - how to think like a pro.
This was the board after 13: Qa4-a3 Rf8-c8
This is the board after 14: Bf1-b5! a7-a6
The moves then went 15:d4xc5 b6xc5 16:O_O Ra8-a7 17:Bb5-a2 Nb8-d7
What I can't figure out is why 14:Bf1-b5! and why the ! He only ends up moving the Bishop back on 17:Bb5-a2. Isn't this losing a tempo and moving the same piece twice with out accomplishing much? I'm trying to understand the reason for this move and can not. More over why did it rate a !(?)
Thanks.
ps. This was from a Chessbase database.