user3570: I just wanted to inquire about the biggest mistake or blunder by Boris Spassky In game no. 6 against Bobby Fischer.

user2569: I am tempted to say "agreeing to continue the match after Fischer's protests!" which some argue was a key psychological defeat.  If you're looking for specific moves that were mistakes, there are a few candidates.  I haven't looked at all annotations, but have Kasparov's My Great Predecessors, vol 4 handy and looking over his notes, it would be either (notations and comments are his):

...d4?
"This move, conceding the important c4-square, was rightly condemned by the commentators.  20. ...Nf6 really was better...but the most accurate solution was the continuation 20. ...c4"

and

...Rb8?!
"The last critical moment."


3570: <p>I just wanted to inquire about the biggest mistake or blunder by Boris Spassky In game no. 6 against Bobby Fischer.</p>
 2569: <p>I am tempted to say "agreeing to continue the match after Fischer's protests!" which some argue was a key psychological defeat.  If you're looking for specific moves that were mistakes, there are a few candidates.  I haven't looked at all annotations, but have Kasparov's <em>My Great Predecessors, vol 4</em> handy and looking over his notes, it would be either (notations and comments are his):</p>

<ol start="20">
<li>...d4?
"This move, conceding the important c4-square, was rightly condemned by the commentators.  20. ...Nf6 really was better...but the most accurate solution was the continuation 20. ...c4"</li>
</ol>

<p>and</p>

<ol start="22">
<li>...Rb8?!
"The last critical moment."</li>
</ol>
