Puzzle of the week #212

Level: 
5-Queen
Chess Diagram: 

[Event "Puzzle #212"][Date "2012.12.09"][Result "1-0"][SetUp "1"][FEN "r2r2k1/p3qpp1/2b1pn1p/2p1B3/7Q/3B4/PPP2PPP/2KR2R1 w - - 0 1"]

White to move is ready for the final assault. All you have to do is:
a) List the reasons why White is ready for the attack
b) Find the best line of attack. Precise calculation is required!

Total available points for this puzzle is 20. The answers will be published next week together with puzzle #213.

Puzzle #211 solution:
Game: John Doknjas (CAN) - Sebastian Zsombor Peczely (HUN) U14 Open WYCC 2012 Maribor, Slovenia. This time it was Leo who put together the best answer:
a) Analyze the position:
It's the end of middle game, as we still see; both sides:
- still have heavy pieces (Queen and Rook) on the board
- have most of their defenders removed; both Kings are open and exposed to the attack
- are searching for the last strike!
Black is better because:
- Overall: both sides have their chances
Black is doing two things at same time: attacking and defending.
White is only doing attacking.
- Though material is equal, in view of King safety, both Kings are open and in danger! Black is in the corner and a bit better as it has some defenders around like Bishop and 2 pawns. The White King is totally exposed without any defenders and in the middle of first Rank
- Direct threat facing: although with the f6-pawn White has a potential checkmate with Qg7 if Black doesn't have Bf8 defending, Black has a powerful Queen and Rook battery on the e-file. To checkmate the White king which has no defenders at all, it is only a matter of time
b) Evaluate the choices for White's next move after Black's last move ...Qe6:
- To play defensively by taking care of White king: not a favourite choice. White could have some game winning chance
- To play 29.Bxf8 ... trying to mate Black: White will eventually lose the game as Black will keep checking until it captures the White Queen
- To play something else: use the strategy of interference
Since White is facing two problems at the same time: to defend its king from the attack launched by Black's Queen-Rook battery and to keep attacking pressure on Black by pursuing checkmate since the Black King, trapped in the corner, has nowhere to go. It's noticeable Ba3 plays an important role in fulfilling both jobs. Also e7 is a critical spot for Ba3; if Ba3 moves to e7, it will interfere with the battery.
So, the best line for White will be:

[Event "Puzzle #211"][Date "2012.12.03"][Result "1-0"][SetUp "1"][FEN "4rb1k/pp3p1p/4qP2/3R2Q1/2p5/B1P3P1/P6P/5K2 w - - 0 1"]1.Be7 {Interference} (1.Bxf8? Qe1+ 2.Kg2 Re2+ 3.Kh3 (3.Kf3 Rf2+ 4.Kg4 Qe2+ 5.Kh4 Rxh2#) 3...Qf1+ 4.Kg4 Re4+ 5.Kh5 Qh3+ 6.Qh4 Rxh4+ 7.gxh4 Qf3+ {Black wins}) 1...Rxe7 (1...Bxe7?? 2.Qg7#) (1...Qh3+ 2.Kg1 Bh6 3.Qe5 {White holds on}) 2.fxe7 {White wins}

Correct solutions:
Leo - 20 points
Daniel - 18 points
Derrick, Justin - 12 points
James - 2 points
Aditya - 1 point

Standings:
James - 119 points
Daniel - 97 points
Derrick - 86 points
Danny - 82 points
Justin - 66 points
Leo - 55 points
Ziyao - 15 points
Richard, Aditya - 10 points
Raymond - 5 points

Comment: 

Storming the castle (10)