White 31

[cheesehead]

[url=http://www.mersenneforum.org/showpost.php?p=375587&postcount=149]30...Nxd2[/url] at 11 Jun 14, 11:21 GMT

Our deadline (with one-hour margin) is Wednesday, 18 Jun 14, 10:21 GMT
= Wednesday, 18 Jun 14, 17:21 Thai time
= Wednesday, 18 Jun 14, 6:21 EDT
= Wednesday, 18 Jun 14, 5:21 CDT

[cheesehead]

Sergey doesn't have the board position posted yet, but ...

I think we're committed to 31 Rxb8 as our next move. :-)

- -

I see our main considerations now as:

1. Black has no near-term threat of attack on our king except the simple ... Bd4+ or ... Nf3+, both of which just lose their attacking piece for no gain as of the current position.

2. The only Black near-term threat to win material (assuming we play 31 Rxb8) is a two-mover: ... Bxc3 followed by ... Bd4+ to win our N/c5 _if_ we haven't moved or protected that knight by then.

3. I think it's best for us to be trading down additional material in the next several moves, getting into simpler end-game positions while eliminating opportunities for Black counter-play, in order to increase our relative advantage.

4. As long as there are pawns on both flanks, bishops tend to be more valuable than knights. Fortunately, our position affords excellent chances of trading our knights for their bishops. OTOH with 30 ... Nxd2 they've chosen the path that gives them the first bishop capture.

5. In the end-game, Black's strongest counter-threat will probably be to advance his a-pawn if he can make that an outside passed pawn. Once we have the material advantage of piece or Exchange, we'll want to make sure we eliminate that a-pawn before it can get strong, perhaps even at the cost of both our queen-side pawns. (With 30 ... Nxd2, Black has chosen the path making it hardest for us to take their a-pawn.)

[cheesehead]

[QUOTE=cheesehead;375598]2. The only Black near-term threat to win material (assuming we play 31 Rxb8) is a two-mover: ... Bxc3 followed by ... Bd4+ to win our N/c5 _if_ we haven't moved or protected that knight by then.[/QUOTE]However,

[B]31 Rxb8 Bxc3[/B] could be followed by:

[B]32 Nb7+[/B] which removes our N/c5 from the checking diagonal.
If [B]32 ... Kc7 33 Nxc8[/B] (Isn't that an interesting formation?) [B]33... Kxb8 34 Nxe7[/B] leaves us up a knight for a pawn. But Black could interpolate instead with [b] [B]33 ... Bd4+[/B] which drives our king into the corner [B]34 Kh1[/B], then [B]34 ... Kxb8 35 Nxe7[/B] again leaves us up a knight for a pawn. There, Black's B/d4 is powerful, but unless Black moves it or his king immediately, 36 Nc6+ Kxb7 37 Nxd4+ will trade it for one of our knights. However, now it's much harder for us to eliminate Black's a-pawn, so maybe we shouldn't go down this path.

Let's go back to my customary presentation of alternatives.

[B]31 Rxc8[/B]

If [B]31 ... Kc7 32 Nxc8[/B]

If [B]32 ... Kxb8 33 Nxe7 Bxc3 34 Nxe6[/B] leaves us up a knight, and deters 34 ... Bxd4+ driving our king into the corner. Then Bc6 and Bb5 ensures that Black will have to trade his knight to eliminate our a-pawn.

If [B]32 ... Nxc8 33 Rb7+ Kd6[/B] (not 33 ... Kd8 34 Rxg7) [B]34 Rxg7[/B] we're up a whole rook. (34 ... Kxc5 35 Rc7+ and 36 Rxc8 also leaves us a rook up.)

If [B]32 ...Bxc3 33 Ra8
[/B]If [B]33 ... Bd4+ 34 Kh1[/B] and nowIf [B]34 ... Bxc5 35 Nxe7 Bxe7 36 Rxa5[/B] leaves us up the Exchange, and it's we who have the outside passed pawn.
If [B]34 ... Nxc8 35 Nxe6+ and 36 Nxd4[/B] we're up a rook.
If [B]33 ... ????[/B]

If [B]32 ... ????[/B]

= =

If [B]31 ... Bxc3 32 ???? [/B](need to copy above [B]32 Nb7+[/B] analysis into here)

= =

If [B]31 ... Be5 32 ???? [/B]

= =

If [B]31 ... ????[/B]

[WMHalsdorf]

31. Rxb8 Be5 32. Nf7+ Kc7 33. Rxc8+ Nxc8 34. Nxe5 {Up a bishop.}

[cheesehead]

Thank you -- incorporated below in updated analysis of Black replies

[B]31 Rxc8[/B]

If [B]31 ... Kc7 32 Nxc8[/B]

If [B]32 ... Kxb8 33 Nxe7 Bxc3 34 Nxe6[/B] leaves us up a knight, and deters 34 ... Bxd4+ driving our king into the corner. Then Bc6 and Bb5 ensures that Black will have to trade his knight to eliminate our a-pawn.

If [B]32 ... Nxc8 33 Rb7+ Kd6[/B] (not 33 ... Kd8 34 Rxg7) [B]34 Rxg7[/B] - we're up a whole rook. (34 ... Kxc5 35 Rc7+ and 36 Rxc8 also leaves us a rook up.)

If [B]32 ...Bxc3 33 Ra8[/B]
If [B]33 ... Bd4+ 34 Kh1[/B] and now
If [B]34 ... Bxc5 35 Nxe7 Bxe7 36 Rxa5[/B] leaves us up the Exchange, and it's we who have the outside passed pawn.
If [B]34 ... Nxc8 35 Nxe6+[/B] and [B]36 Nxd4[/B] - we're up a rook.
If [B]33 ... ????[/B]

If [B]32 ... ????[/B]

= =

If [B]31 ... Bxc3[/B]

If [B]32 Nb7+[/B] removes our N/c5 from the checking diagonal.
If [B]32 ... Kc7 33 Nxc8[/B] (Isn't that an interesting formation?) [B]33... Kxb8 34 Nxe7[/B] leaves us up a knight for a pawn. Black could interpolate
If [B]33 ... Bd4+ 34 Kh1 Kxb8 35 Nxe7[/B] again leaving us up a knight for a pawn. There, Black's B/d4 is powerful, but unless Black moves it or his king immediately, 36 Nc6+ Kxb7 37 Nxd4+ will trade it for one of our knights. However, now it's much harder for us to eliminate Black's a-pawn, so maybe we shouldn't go down this path.

If [B]32 ????[/B]

= =

If [B]31 ... Be5 32 Nf7+[/B]

If [B]32 ... Ke8 33 Nxe5[/B] and we're a whole rook up.

If [B]32 ... Kc7 33 Rxc8+ Nxc8 or Kxc8[/B] (not 33 ... Kb6 34 Nd7+ Ka6 or Ka7 35 Re8 - another interesting formation) [B]34 Nxe5[/B] and we're up a bishop.

= =

If [B]31 ... ????[/B]

[cheesehead]

[QUOTE=cheesehead;375628]
= =

If [B]31 ... Bxc3[/B]

If [B]32 Nb7+[/B] removes our N/c5 from the checking diagonal.
If [B]32 ... Kc7 33 Nxc8[/B] (Isn't that an interesting formation?)[/QUOTE]If [B]33 ... Nxc8 34 Ra8[/B] threatens to get our rook out via a6 (or capture the pawn on a5). Black can't prevent that rook escape by 34 ... Kb6 without losing the N/c8, and of course 34 ... Nb6 (or Na7[sup]*[/sup] or Ne7) allows escape on the eighth rank. If 34 ... Nd6 we should take on a5 (35 Nxa5) rather than swap knights.

[sup]*[/sup] Remember that after 34 ... Na7, 35 Rxa7 Bd4+ would give back our Exchange material advantage. Then after 36 Kh1 Bxa7 37 Nxa5 our remaining advantage, that outside passed a-pawn, already has the Black king and pieces poised to eliminate it. In fact, Black has the independent threat of his own passer: [speculation] 37 ... e5 38 Nc6 Bd4 39 Nxd4 exd4 40 Kg1 d3 41 Kf2 Nc4 42 Ke1 d2+ 43 Kd1 Ne3+ 44 Kxd2 Nxg2 45 Ke2 Kb6 46 Kf2 Nh4 47 gxh4 Ka5 48 Ke3 Kxa4 49 Ke4 Kb4 50 Ke5 Kc4 51 Kf6 Kd4 52 Kxg6 Ke5 53 Kxh6 Kg6 54 Kh7 Kf7 55 h5 Kf8 56 Kg6 Kg8 draw.

[WMHalsdorf]

31. Rxb8 Bxc3 32. Nxe6+ Kd7 33. Nxc8 {Black has no goof choices.}

[cheesehead]

[QUOTE=WMHalsdorf;375650]31. Rxb8 Bxc3 32. Nxe6+ Kd7 33. Nxc8 {Black has no goof choices.}[/QUOTE]I had just discovered that, too!

- - -

Folks, I'm tired now, so am taking a break. I hope it's better for me to post my analysis in its current state than wait until I finish more.

Your suggestions, if any, for improving my format for easier comprehension would be welcomed! :-)

- - -

(Note: If Black doesn't play 31 ... Bxc3 so soon, perhaps we could find time for Kf2 so as not to be confined to the h1 corner by ... Bd4+.)

- - -

[B]31 ... Bxc3 32 Nxe6+[/B] which leaves Black only one legal move: [B]32 ... Kd7[/B] (How often does one see a player force his opponent's king to attack two of his undefended pieces, while simultaneously unpinning another of the opponent's pieces?)

If [B]33 Nxc8[/B]

If [B]33 ... Nxc8 34 Bh3[/B]

If [B]34 ... Ne7 35 Rb7+[/B]

If [B]35 ... Kd6 36 Nc7[/B] threatens Nb5+
If [B]36 ... Kc6 37 Bg2+[/B]
If [B]37 ... Kc5 38 Nb5[/B] attacks the N/e7 and B/c3.
If [B]38 ... Nd5 38 Bxd5[/B]
If [B]38 ... Kxd5 39 Nxc3+[/B].
If [B]38 ... Bd4+ 39 Nxd4[/B] .
If [B]37 ... Kd6 38 Nb5+[/B] wins the B/c3.

If [B]35 ... Ke8[/B]
If [B]36 Nc7+[/B]
If [B]36 ... Kf8 or Kf7 37 Nb5 ????[/B]
If [B]36 ... Kd8 37 Nb5[/B] threatens 38 Rb8+ Nc8 39 Rxc8+ and 40 Rxc3

If [B]34 ... Nd6 35 ????[/B]

- - *

If [B]33 ... Kxe6[/B]
If [B]34 Bh3+[/B]
If [B]34 ... Kf7[/B]

- -

If [B]35 Rb7[/B] pins the already-attacked N/e7 and threatens to capture it.
If [B]35 ... Bb4[/B]

- -

If [B]35 Nd6+[/B]

If [B]35 ... Kf6 36 Rf8+[/B]

-

If [B]36 ... Ke5 37 Nf7+[/B]
If [B]37 ... Kd4 38 Nd6[/B] threatens Nb5+
If [B]37 ... Kd5 38 ????[/B]
If [B]37 ... Ke4 38 Re8[/B]
If [B]38 ... Bb4 39 ????[/B]
If [B]38 ... Bd4+ 39 Kg2 Bc5 40 ????[/B]
If [B]37 ... Kf6 38 Nxh6+ Kg7 39 Rf7+ Kxh6 40 Rxe7[/B] We're up a rook and pawn for a knight.

-

If [B]36 ... Kg5 37 ????[/B]

-

If [B]36 ... Kg7 37 Rf7+[/B]
If [B]37 ... Kg8 or Kh8[/B] (the following analysis/speculation applies after either king move) [b]38 Rxe7[/b] Now [B]38 ... Bb4[/B] seems Black's best move.
If [B]39 Rd7 or Re6[/B] We're up a rook.
If [B]39 Re8+ Kg7 or Kh7[/B]. We're up a rook, but mustn't forget about the B/b4 attack on our N/d6.

- -

If [B]35 ... Kg7[/B]

- - -

If [B]35 ????[/B]

- - - -

If [B]34 ... Kf6[/B]

- -

If [B]34 ... Kd6[/B]

[cheesehead]

Briefly,

[QUOTE=cheesehead;375598]5. In the end-game, Black's strongest counter-threat will probably be to advance his a-pawn if he can make that an outside passed pawn. Once we have the material advantage of piece or Exchange, we'll want to make sure we eliminate that a-pawn before it can get strong, perhaps even at the cost of both our queen-side pawns. (With 30 ... Nxd2, Black has chosen the path making it hardest for us to take their a-pawn.)[/QUOTE]After going over some scenarios, I think this (promote their a-pawn) indeed is Black's best hope.

31 ... Bxc3 fits right in with that.

[cheesehead]

I think we should go ahead and post [B]31 Rxb8[/B]. It's completely obvious, and the sooner we post it, the sooner we find out how Black replies.

- - -

Anyway, it's hard for me to focus on analysis now. I'm dealing with the aftermath of a water leak (now stopped, but ...) in my apartment.

[LaurV]

Sorry to hear about the leak.
Agree about posting the move. It is obvious, as it is same obvious that we won this game, looking to the versions you both posted, there is no way we don't get out of this with a figure. And then I make my Sunday free, no need to think to chess anymore.