At first I was thinking that 18...Qh4 was the most appealing. However, 19.Rg1 Qh3+ 20.Rg3 Qh1+ 21.Rg2 Qh5+ 22.Rg4 f5 23.Bxf5 Rxf5+ 24.Kg2 Qh2+ 25.Kf1 and it seems the king escapes.

It really seems to come down to 1 of 2 moves (Qf6+ or Qg5) and neither one seems immediately clear.

18...Qf6+ 19.Kg4 Qe6+ 20.Bf5 h5+ 21.Kg5 (else lose the bishop) f6+ 22.Kg6 Qe8#

18...Qf6+ 19.Kg4 Qe6+ 20.Kh4 Bd8+ 21.Kg3 doesn't seem clear.

So let's try 18...Qg5:

19.e4 Qh5+ 20.Ke3 Bf4+ at least wins the queen.

19.e4 Qh5+ 20.Kg2 Qh2+ 21.Kf3 Qh3#

19.Qd1 Qh5+ 20.Kg2 Qh2+ will at least draw.

19.Rh1 h5 20.e4 Qg5+ 21.Ke3 Bf4+

And now one more look at the original 18...Qh4:

19.Rg1 Qh5+ 20.Rg4 f5 21.Bxf5 Rxf5+ 22.Kg2 Rg5 23.f3 Qh2+ 24.Kf1 - it's getting a bit cloudy.

18...♕f6+ continues the attack initiated by the ♘ and ♗. It keeps the king out in the open and except for the b2-h6 diagonal and the g3 and f4 squares White has no say on the king side.

17.♔g2? was a real stinkeroo. White already has problems but is only losing marginally and can still make a draw. After this Petrov is emboldened to attack away. Sometimes its good to hold a pin as I believe it was Nimzowitsch who said, "The threat is stronger than the execution." But not this time as Bug's Bunny would say!

17...♗x♘f3 showed true grit. Did the GM really calculate to a win or just figured a draw at least was there. I calculated five variations after queen move and wasn't sure all led to free queen and bishop or mate. I was sure that every continuation was winning though.

Very good study indeed! The most enjoyable part is finding the best defenses for White.

Analysis Calculation Execution: Study (ACE's)

1) My static evaluation was that white is better materially but the openness of the white king suggested there could be something better. According to Steinitz, there is no winning move unless the position is winning. So given my evaluation and uncertainty, I was perfectly willing to settle for a draw and 18...Qg5 seemed to secure this.

2) It was hard to decide between the three candidates: Qf6+, Qg5, Qh4. I became convinced that 18...Qg5 could draw but had some difficulty visualizing everything after 19.e4 so until I understood that it lost simply to 19...Qh5+ 20.Ke3 Bf4+ I couldn't be happy with this. There was another concern here, like 19.Rh1. It could prove good or bad, so the result of getting "at least" a draw is unclear until you examine moves like 19...h5 for example. Here's another way of looking at this: If white can definitely secure a draw, then that is black's best result. But that doesn't guarantee black will not lose! So really this is a good indicator to look at another primary candidate, to see if there is a better result.

3) After examining 18...Qf6+, visualization is ultimately what failed me. As <agb2002> suggested in line B.2), 20.Kh4 g5+ 21.Kxg5 (which I considered) Kh8 (the move I failed to see) and it's why I dismissed the whole line!!

In essence, I tried to do all the right things and still came up short. What can I say?

<morf>/<goodevans> - I also considered 18...Qh4 19.Bf5 and found it unclear except something like 19...g6 20.Bg4 h5 seems good for black. But white can guarantee a draw with 19.Qd1! as in the 18...Qg5 line. The only question is, does white want to do this given his material edge? It seems that can only be answered with more analysis, but black won't get anything better than a draw.

After analyzing with the help of the other great commentary here, I see that Qf6+ IS the best move. A SIMPLE way of looking at it is after Qf6+ white has to play Kg4 because Kg2 allows the black queen, with support of the dark squared bishop on c7, to mate on h2. Pointed out nicely by M. Hassan. After Kg4 it's easy to see the king is offsides.

< Yes Ed, a great example is Bobby Fischer's play. He reduced his opponents counterplay to nothing. He regularly achieved this even at the cost of his own activity. Almost as if his first goal was to squeeze his opponent on his own terms, while eliminating his chances of losing.>

(1) <Visualization> I looked at both 18...Qf6+ and 18...Qh4 before I even realized Black was down material! This is not good problem-solving and is a good example of the difference between playing and solving (ie: a player actually arriving at this position in a real game would know if he's up or down material). Also, since I had overlooked the material deficit, I suspected I may have overlooked "other stuff" and gave the board a once-over and only then noticed the tactic against the White Queen: Its "hanging" on <e2>. Oh boy, thats a lot of stuff to overlook prior to trying to solve a problem.

(2) <Tactics> On candidate moves, I like to analyze them all, at least a little. Of course, if I find a forced win, I'll stop there and re-check the line to confirm its sound or really "forced". If it wins, I'll only look at the other candidates "for the fun of it". In this problem, I didn't initially appreciate the full forcing nature of 18...Qf6+ and so moved onto 18...Qh4; and here, I then didn't "see" the best moves for White! (Note: 18...Qh4 is temptingly deceptive, almost wicked in its attractiveness due to the dual threat 19...Qh3# and 19...Qg4+ forking the hanging Queen. Dual threats like this, that attack both King and Queen, can distract one from the best move, which in this case, was 18...Qf6+)

Conclusion: Examining checks, captures and forcing moves first is the most efficient method. However, from both a material and positional aspect, "initial board awareness" is critical too. I came up way short in these categories