A 'Forced Move' That Wasn't Best

The next critical position in Fischer - Reshevsky, Match 1961 (Game 5), is worthy of a Larry Evans style What's the Best Move? multiple choice. White played 21.Nb5. Now what's the best move?

• 21...Qxe3
  
• 21...Qd5
  
• 21...Qxb2

It's not easy to choose because the variations are all tactically complicated.

1961 Match (game 5)
Fischer, Robert

Reshevsky, Samuel
(After 20...Qd8-d4(xP))
[FEN "2r1r1k1/pb5p/1pn1p1p1/5pN1/3q1n1P/P1N1Q3/1PB2PP1/2R1R1K1 w - - 0 21"]

After 21.Nb5, Fischer wrote,

Marvelously alert! After the practically forced trade of Queens, White wins the exchange because of the imminent fork on e6.

The phrase 'forced trade of Queens' tells us that Fischer's choice of best move was the move he played: 21...Qxe3. The game continued 22.fxe3 Nxg2 23.Kxg2 Nd4+ 24.Be4 Bxe4+ 25.Nxe4 Nxb5 26.Nf6+ Kf7 27.Nxe8 Rxe8 28.a4 Nd6 29.Rc7+ Kf6 30.Rec1 h6 31.Rxa7 Ne4 32.Ra6 Rd8, where Fischer concluded that Black is now fighting for a draw. Kasparov pointed out that 23...Nb4+ would give Black 'more chances of saving himself than in the game'.

Fischer also mentioned 21...Qd5.

After the game we analyzed 21...Qd5 22.Qxf4 Qxb5 23.Nxe6 Qxb2 (23...Qd5 24.Nc7 Rxe1+ 25.Rxe1 Qf7 26.Ne6) 24.Qh6 with an irresistible attack: 24...Na5 (24...Rxe6 25.Rxe6 Nd4 26.Re7) 25.Bxf5 gxf5 26.Rb1, giving as a variation 25...Rxc1 26.Rxc1 gxf5 27.Rc7.

Kasparov, in turn, showed that 26...Qf6 is better than 26...gxf5 in that last variation, and concluded that the win is 'problematic'. This makes 21...Qd5 better than 21...Qxe3. For his part, Kasparov considered that Dvoretsky's 21...Qxb2 was best.

21...Qxb2 22.Nd6 Nxg2 23.Kxg2 Nd4+ 24.Be4 fxe4, leads to a double-edged game.

The sequence 25.Rxc8 Rxc8 26.Nxb7 fails to 26...Nc2. He also analyzed 25.Nxb7 Nf5 to an endgame where Black is not worst, and 25.Rb1 Qa2 leads to a middlegame where Black's attack is just as ferocious as White's, allowing Black to draw.

I spent a lot of time looking at 21...Qxb2, and convinced myself that Kasparov's analysis was airtight. Black gets good counterplay, making it the best of the three choices. Fischer didn't even mention it. What did he overlook?