Puzzle of the week #138

Level: 
4-Rook
Chess Diagram: 

[Event "Puzzle #138"][Date "2010.10.25"][Result "0-1"][SetUp "1"][FEN "2r3k1/3bpp1p/3p1npQ/4q3/rp1NP1P1/5PN1/PP5P/1K1R2R1 w - - 0 21"]{Game line} 21.Ngf5 Nxe4 22.Qe3 gxf5 23.gxf5+ Ng3 24.Rxg3+ Kh8 25.Qg5 Ra5

Another opposite wing attack from the Olympiad should convince you: if you want a good result, you need to take calculated chances/ risks. Rarely the opponent will roll over nicely and let you win the game. You must take it from him! In order to do that you need to play well in all aspects of the game. Attacking and defending should be done with focus and precision. See diagram for a small sample of how the position was played. Your tasks:
a) Explain the move sequence above
b) White looks again at his defence 26.Qd2 ... What should Black do?

Total available points for this puzzle is 20. The answers will be published next week together with puzzle #139.

Puzzle #137 solution:
Game GM Corrales Jimenez, Fidel (Cuba) - GM Stellwagen, Daniel (Netherlands), 39th Chess Olympiad 2010 Khanty Mansiysk, Russia. This time we have an excellent solution from Karl.
a) Analysis:
Material: Black has an extra pawn.
King safety: The Black King is a bit safer. The White King is not defended very well on one side.
Position: pieces of both sides are all developed and all have good mobility: Rooks are on semi-open files, Knights are both active and the Queens can be used easily (well, after a few moves the black queen can).
White has a battery on the e-file, looks menacing with the Knight extended and the pieces pointing towards the White King. Black is defending instead.
Conclusion: White seems to have a better position, but it all comes down to the moves.
Plan for White: Win some material by taking advantage of the e- and f- files, and try to get a attack going.
Plan for Black: counterattack on the Queenside and try to checkmate Black or win some material.
b) See solution

[Event "Puzzle #137"][Date "2010.10.18"][Result "0-1"][SetUp "1"][FEN "3rr1k1/p3bppq/2p1p2p/3nN2P/2pP4/2B2R2/PP2QPP1/2K1R3 w - - 0 24"]24.Nxf7 {Solution:} 24...Nxc3 {Distracting the defender; if White goes 1... Rxc3, then black wins Nf7} 25.bxc3 Rb8! 26.Qe4 {The only move to stop a devastating check on b1} 26...Ba3+ 27.Kd2 Rb2+ 28.Ke3 {Game line} (28.Kd1 Rb1+ 29.Kd2 Bc1+ 30.Kc2 (30.Rxc1 Qxe4 {Black wins}) 30...Qxe4+ 31.Rxe4 Reb8 32.Kd1 Bf4+ 33.Ke2 R8b2#) 28...Re2+!! 29.Rxe2 Bc1+ 30.Rd2 Bxd2+ 31.Kxd2 Qxe4

Correct solutions:
Karl - 20 points
Jeffrey, Alex, Nathaniel - 10 points

Standings:
Karl - 210 points
Jeffrey - 197 points
Rick - 174 points
Frank - 122 points
Owen - 95 points
Alex - 81 points
Edwin - 72 points
Nathaniel - 50 points

Comment: 

No second chances