The key issue in this game, as noted by popski and others on this site, is why Didier didn't simply play 12. QxR. As I will show, Didier could and should have played 12. QxR and could and should have won had he done so.

Before addressing this question, however, the events leading up to Didier's mistake on move 12 must be addressed.

1. e4 d5

The Center Counter Game.

2. exd5 Qxd5
3. Nc3 Qa5
4. d4 c5?!

Normal and best here is 4...Nf6. I see little other than originality to recommend Mieses' strange alternative. If he wanted to try an off-beat agressive challenge to White's control of the center, Anderssen's 4...e5?! was a possibility.

5. dxc5 e5?!

Rosenthal in the Tournament Book appropriately labeled this move as "weak." His suggestion of the simple 5...Qxc5 seems best, though White would still be much better after 6. Be3

6. Be3

6. Nf3 was better, though the text is sufficient to maintain White's strategically won position.

6... Bxc5?

Very bad. Mieses should have anticipated Didier's next move with 6...Nf6.

7. Bb5+

"Very well played." (Rosenthal in the Tournament Book).

7... Bd7
8. BxB(c5)

Rosenthal is correct that 8. Qd5 would also have given an overwhelming advantage. The text, however, is best.

8... BxB

9. h4

Very strong, but even better was an immediate 9. Qg4.

9... Qa6
10. Qg4

Rosenthal correctly notes that White could win with 10. Ne4, since 10...Ne7 (10...Nd7 is "best" here, but 11. Nd6+ would still be crushing) 11. Nd6+ Kf8 12. NxB QxN 13. Qd8+ is mate in two. But the text also wins, and--with best play--even more decisively.

10... Nd7
11. Qxg7 0-0-0

We now arrive at the crucial position of this game that has been discussed on this site:

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The short answer to whether Didier should have played 12. QxR is an emphatic "Yes." This move wins in all variations.

Mieses would have had two possible responses had Didier played 12. QxR. Neither would have been sufficient.

1) The only move considered by Rosenthal in the Tournament Book after 12. QxR is 12...Ngf6. Didier would then of course have played 13. Qg7, leaving Mieses two plausible continuations, both of which would have lost:

A) 13...Rg8 as given by Gambit All on this site. But this gets crushed by 14. Qxf7.

B) 13...NxB

This move (recommended by Rosenthal in the Tournament Book) is probably best in this position, but totally inadequate. If White responds 14. bxc5, then Black indeed can claw his way back into the game with (following Rosenthal's line) 14...Qa5 15. Nge2 BxN 16. KxB QxN 17. Rhd1 Qxc2+ 18. Ke1 Qe4+ 19. Kf1 Rg8.

But instead of 14. bxc5, White can win with 14. NxB. According to Rosenthal, Black now comes out on top, but his analysis is flawed. He recommends 14...Nce4 and then if 15. c4? Qa4 16. a3?? Qc2 with a win for Black. But White should play 15. a4 in this line leaving him a Rook ahead and a winning position. Even on 15. 15. c4? Qa4, White can still win with 16. Ne2 (instead of the disastrous 16. a3? given by Rosenthal) 16...Qxb4+ 17. Nec3 NxN 18. 0-0

Black has better chances in this line with 14...QxN (instead of Rosenthal's 14...Nce4) but this still loses after 15. QxN Qxb4+ 16. Kf1 Qc4+ 17. Ne2 Qxc2 18. g3 with White up a Rook for a pawn and an easy win.

II) The best chance for Black seems to be 12...NxB as suggested by ounos on this site. Had White then played the tempting 13. bxc5 then Black could have saved the game with 13...Nf6 (and not with ounos' 13...Qa5 which loses to 14. Nge2 and then if 14...BxN 15. Qxe5 and if 14...Nh6 15. Qg7.

If Black plays 13...Nf6 in ounos' line, then White's win is gone: 14. QxN QxQ 15. NxN leaving the following position:

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Chances here seem to me to be about even.

However, after ounos' 12...NxB 13. Rd1 wins for White;

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In summary, Didier had a win with 12. QxR.

After Didier missed 12. QxR and played 12. Rd1?, the position was as follows:

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His mishap notwithstanding, Didier still had the better chances. The play from here on, however, was extremely sloppy:

12. Rd1 Ngf6

Mieses' Rook is now no longer hanging.

13. Be7 Rdg8
14. Qh6?

Very bad. Didier would still have had much the best of it (even if not a winning position) with the obvious 14. Qxf7. By now, however, it is apparent that Didier was seeing ghosts.

14... Bc4?

Mieses errs in turn. He would be fine after 14...Bc6.

15. a4?

Didier fails to exploit Mieses' error. He should have played 15. Qe3. Indeed, if that was not his intention, why did he play 14. Qh6 instead of 14. Qxf7?

15... Qc6!

All of a sudden, Didier is in trouble. The weakness on g2, which Mieses should have targeted on his last move, now becomes a terrible problem for Didier.

16. Nf3

Perhaps 16. Qe3 was slightly better here.

16... Rxg2

The position was now as follows:

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Didier could probably have held this game had he played 17. Qe3. But instead he played:

17. Qh3?

Now, Mieses has a lovely winning combination beginning with 17...Be6!!. If then 18. QxR (what else!) Rg8! Didier would now be dead since if 19. Rf1 QxN+ 20. Nd2 Rg4! and wins (White is nominally up the exchange, but his position is clearly untenable).

But Mieses missed 17...Be3!! and instead played:

17... Rg6?

Now, Didier is back in the game. He found the saving move here.

18. Rd6!

Now, White also has threats, and nearly equal chances.

18... Qc7

Forced!

Didier is very much back in this game. Nevertheless, he managed to lose in just three moves.

After Mieses' 18...Qc7, the position was as follows:

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In this position, Didier played the awful:

19. Nxe5??

Walking into a deadly pin with 19...Re8. Rosenthal correctly notes that 19. RxN would not have saved the game for Didier here, but his analysis is flawed. He claims that after 19. RxN Black wins with 19...RxR 20. BxR Be6. That may be true, but after 21. Nb5! BxQ 22. NxQ NxB 23. Ng5 KxN 25. NxB Rg8 the position would be:

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Black may indeed be able to win this endgame, but it's hardly a cake-walk.

However, Black had a clear win after 19. RxN with 19...Be6!! threatening 20...QxN+. Now, if 20. Nb5 BxQ 21. NxQ NxR and wins.

But Didier could have avoided all these problems with 19. Nh4! with about equal chances.

After Didier's actual move, 19. Nxe5, the game ended very quickly.

19... Re8!

A remarkable kind of pin/skewer!

20. RxN?

If Didier wanted to continue, he had to play 20. RxN, though with little hope of survival.

20... RxB?

The text wins, but 20...QxN+ is obviously even more crushing.

21. Rf5?

21. RxR was the only hope of prolonging the struggle.

21... RxN+

This move ended the game successfully for Mieses, but he should nonetheless have played the beautiful winning move 21...Kb8!!! This move maintains the pin on the e-file and frees the d7 Knight from the pin on the h3 c8 diagonal, leaving the position as follows:

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