1. d4 g6

Rosen was 2-11 going into this game, and apparently decided to try something unorthodox (a "creative" version of the King's Fianchetto Defense) against his more talented opponent. This did not go well for him.

2. e4 e6?!

2...d6 or 2...Bg7 could lead to a Pirc Defense. Another reasonable option noted in MCO-13 is 2...c6.

The text creates serious weaknesses in Black's position (e.g., d6 and f6--the latter ultimately resulting in Rosen's defeat here).

3. Bd3

This is not bad, but the simple 3. Nf3 or 3. Nc3 were better.

3... f5?!

This wild and crazy move fatally compromises Black's position. Rosen would have had a reasonable game with 3...Bg7 or 3...d5.

4. Nf3

4. exf5 was much stronger. The text needlessly allowed Black to undo some of the damage from his last move by trading off his f-pawn without displacing his e or g pawns. But Rosen did not avail himself of his chance here.

4... Nf6?

4...fxe4 was the last chance to salvage his position.

5. exf5

Another strong move for White here was 5. e5

5... exf5

He might have tried 5...gxf5, but would still suffer from his previous poor play.

6. 0-0 Bg7?

"Weak. The right move was 6...Be7." (Rosenthal in the Tournament Book).

While Rosenthal was most definitely correct that 6...Bg7? was weak and also correct that 6...Be7 would have been much better. But perhaps best was the ugly looking 6...Kf7. Like it or not, Rosen's king had to run for his life.

The ugly position in which Rosen now found himself was:

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7. Re1+ Kf8

Rosen's King runs, but to the wrong square. 7...Kf7 was less disastrous than the text.

8. c4

8. Nc3 was another way to pile up the pressure on Rosen.

8... d6

He might have considered 8...Nc6, but would still have been in a shattered position.

9. Nc3

Having said "A" (8. c4) he should have continued with "B" (9. c5).

9... c6

This only created new weaknesses. Rosen should have anticipated the coming King-side attack with 9...h6 or 9...Kg8, although his army would still have been fatally compromised.

The position was now:

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Obtaining a theoretically winning position is one thing. Being able to convert such an advantage and actually win the game is another. For quite a while in this game, Showalter had problems accomplishing the latter task.

10. Qe2

White had many good plans at his disposal here (10. Bf4; 10. Qb3; 10. d5). The text, while not losing all of Showalter's advantage, was not among them.

10... Na6

Rosen apparently decided to play to trade off White's b3 Bishop for the thus far inactive Black Queen's side Knight. This plan, however, could have been easily countered, and 10...h6 or 10...Kg8 arranging for the protection of the Black King were better.

11. Bf4

11. c5 was another good idea here, but the text which develops the dark-square Bishop was also good.

11... Nb4

Continuing with his questionable plan. 11...Nc7 or 11...Kg8 were better.

12. Rad1

Showalter should probably have made sure to preserve his Bishop with 12. Bb1, awkward as that looks. If he didn't fancy doing that, he should have played something more productive such as 12. d5. The text, which makes room for the Bishop to retreat without locking in the a1 Rook only works if Black fails to trade on his next move.

12... h6

Given Rosen's 10...Na6 and 11...Nb4, it is hard to see why he didn't play 12...NxB here.

13. c5

Once again, Showalter should either have preserved his Bishop with 13. Bb1 (especially since that move--thanks to Rosen's 12...h6) will not lock in his Rook). Alternatively, he should have played 13. d5.

13... d5
14. Bb1

Finally! His alternative here was 14. Ne5.

14... Kg8
15. a3

Once again, Ne5 was a reasonable alternative. But the text has the merit of driving away the pesky Black Knight at b4 and causing Black to lose time.

15... Na6

Now, after Rosen's ill-advised Knight venture, the position was:

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Showalter still has much the better position. But how should he continue:

16. Rd3

This effort to pile up his heavy pieces on the e-file can't have been best. The Pillsburyish 16. Ne5 looks best.

16... Ne4

Thanks to Showalter's dawdling, Rosen has managed to create a difficult but probably defensible position for himself.

16...Nc7 was another good alternative.

17. Be5

The alternative was 17. Ne5. In either case, Black is not without resource.

17... Rh7

A poor and wasted move that deprives Black's King of possible refuge on h7. Better were 17...Nc7 (perhaps finally getting the a6 Knight into the game) or 17...Kh7.

18. BxB?

There was no reason to ease Rosen's defensive burdens by this exchange. 18. Ba2 (exploiting the position of the Black King) or 18. Re3 (following up on his questionable 16. Rd3) were better.

18... BxB
19. Ne5 Nc7
20. f3 Ng5
21. Qd2 h5

21...Qf6 or 21...Kh7 were better.

22. Ne2

Bringing this Knight to the King-side where it could have decided the game in White's favor (thanks to Rosen's poor 23rd move) in short order.

22... Nce6
23. Nf4

The position was now:

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Rosen had been gamely struggling to hold on in a poor position for about 20 moves. But his poor 23rd move should have led to immediate disaster.

23... Qf6?

The position was now:

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White to move and win.

24. NxN?

Both the players and Rosenthal in the Tournament Book missed White's win here: 24. Nexg6! winning a pawn with an overwhelming position. Had Black played 24...RxN he gets crushed with a devastating pin on the g-file: 24...RxN 25. NxR QxN 26. f4! Ne4 27. RxN followed by 28. Rg3 winning the Queen.

Showalter's placid Knight trade, by contrast, puts Rosen back in business.

24... BxN
25. Rde3 h4
26. h3

26. h3 or 26. b4 were the only ways to retain anything close to the winning advantage Showalter has enjoyed for most of the game.

26... f4

Courting trouble. 26...Re8 was simpler and better.

27. R3e2 Rf8
28. h3

The position--that proved to be the critical position in this game-- was now:

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28... Bf5?

"A mistake which compromises his game. Correct was 28...Bc8..." (Rosenthal in the Tournament Book).

After Rosen's ill-judged 28...Bf5? the position was:

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29. BxB

As Rosenthal pointed out in the Tournament Book, White also can win with 29. Qxf4 BxB 30. QxQ RxQ 31. RxB [31. Ng4 is even stronger] Rf4 32. Rd1 (or the better 32. Ng4 or 32. Rbe1) leaving White a pawn ahead. The text, however, is a much better line.

29... QxB?

29...gxN would probably not have saved the game, but it at least have kept White's Knight from moving to g4 where it is poised for any one of a number of winning Knight forks.

30. Ng4!

Decisive.

30... Nf7?

Locking in his King and equivalent to resignation. In fairness to Rosen, however, and as Rosenthal pointed out in the Tournament Book, Black's "better" options would also have led to defeat: (a) 30...Qd6 31. Re8 Nh7? [31...Rgf7 was less immediately disastrous, but also hopeless) 32. RxR+ KxR 33. Qxf4+; or (b) 30...Qc8 31. Re8 (31. Nf6+ also wins) RxR 32. RxR+ QxR 33. Nf6+.

Showalter is now poised for the grand finale, the position now being:

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white to move and win:

31. Re5!

A lovely move which ends the game quickly.

31... NxR

Other moves also lose, e.g., (as per Rosenthal's commentary) 31...Qc8 32. Nf6+ Kh8 33. Qxf4 g5 [this leads to a pretty mate in four, but everything else also loses] 34. Qxh4+!! gxQ 35. Rh5+ and mate in two (Rosenthal).

After the text, Showalter finished nicely:

32. Nh6+ Kh7
33. NxQ Nc4
34. Qxf4 RxN
35. Qxh4+ Rh5
36. Qd8