Well, the more I look at this, the more I feel that the black king is not subject to direct attack (things like 30 Bh6+ pretty much go nowhere).

Once the king is eliminated as a target, the only thing in black's position that looks dicey is the knight. It is pinned against the black queen in such a manner, that black cannot break the pin without dropping the horse.

With that in mind, I would like to attack the knight with another piece and win it outright. But, black can play ...e5 putting another defender on the piece (and a pawn at that). Therefore I think white's first move should be

30 Be6

blocking the e-pawn. Black still can't move the knight without losing the queen, so next move I plan to play 31 Rad1. Is there anything black can do? I suspect he will play something like

30...Nxe6 31 Bxb6 Bxa1

But now

32 Rxa1 Rxb6

allows the coup de grâce

33 Qd4+ and 34 Qxb6.

33 Qd4+ and 34 Qxb6. >

Qd4+ is not possible because of the black knight at e6

click for larger view

Rybkav2.3.2a.x64:

(23-ply)
1. (2.45): 30.Be6 Qc5 31.Rfd1 Nxe6 32.Bxc5 Nxc5 33.Qe3 a4 34.Ra3 Rb7 35.Qd2 Rc7 36.Kg2 Ne4 37.Qb4 Rfc8 38.Rc1 Nc5 39.h4 Rb7 40.Rd1 Rb6 41.Rh1

2. (2.20): 30.Rfd1 e5 31.Bd2 e4 32.Qe3 Be5 33.Bxa5 Qc5 34.Ra2 Rfc8 35.Bc3 Nxb5 36.Qxc5 Rxc5 37.Bxe5+ dxe5 38.cxb5 Rcxb5 39.Kg2 Rb2 40.Rda1 Kh6 41.Rxb2 Rxb2 42.Ra2 Rxa2

3. (2.01): 30.Rfb1 e5 31.Qd2 Kh8 32.Bh6 Rfe8 33.e3 Ne6 34.Qxa5 Nc5 35.Qxb6 Rxb6 36.Ra7 e4 37.Kg2 Bc3 38.Bg5 Reb8

1)30.Be6, because it seemed a nice square for the bishop and the black N couldn't take it. Unfortunately I thought this should be followed by some weird attack or sac, like 31.Bxf5, but it made no sense. 2)30.Rfd1, to attack the pinned piece. Of course this was a beginner move because Black can safely play 30..e5.

Afterwards I wondered, "What would Tal do?" and thought of some crazy attacks like 30.Rxa5 Qxa5 31.Bxd4 Bxd4 32.Qxd4+ , but after 32..e5 White has nothing, he just lost the exchange for a pawn.

Unfortunately I missed the obvious connection between my first 2 candidate moves. 30.Be6 is the conditio sine qua non to attack the pinned N with a rook!

30.Be6

removing the possibility of solid reinforcement for the N with e5.

The various defenses fail.

31.Ne7+ or Nf6+ throws the N for at most a P

31.d4 cxd4 threatening Rad1 to finish the N, with the threat Bxd4 followed by Bxf6+ robbing Black of the tempo required to relieve the pin by moving the Q.

Time to peek. The game continuation required more patience than I had for the analysis today, but it does make clear why this was a Friday puzzle.

I would welcome <thoughtful> insights from practical players on how much Uhlmann calculated over the board. The absence of any real possibility other than 30.Be6 made the move seem easy to choose and play.

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Initially considered Rfd1, but after seeing that the reinforcement allows e5, I would have instead played Rad1. After 30 Rad1 e5 (forced) 31 f4 then forces open a file for attack, since 31 ... e4 loses the knight after 32 Qd2 (careful, careful - 32 Qc3? Nxe2+ 33 Kf2 Nxc3 34 Bxb6 Nxd1+ and White loses a Rook. Even if 33 Kg2 instead, so Nxd1 is not check, White still loses the Rook since he can't both save his Bishop and take Black's Knight).