rnbqk2r/p1pp1pbp/1p2p1pn/4P3/2BP4/5Q2/PPP2PPP/RNB1K1NR w KQkq - 0 1
Is the rook sacrifice intended by the black to trap white's queen or is it just a misplayed move?
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Is the rook sacrifice intended by the black to trap white's queen or is it just a misplayed move?
In general, it's very hard to trap a queen like that. After Qxa8 Nc6, the white queen can't escape immediately but it's not hard to devise an escape plan; with Bb5 White threatens to exchange the only defender of the a7 pawn, and at the same time winning another pawn on c6. So my conclusion is that Black's last move was a blunder.
It may have been a misguided attempt to trap the queen, but since there is no immediate follow-up threat against her, she will have time to escape, in which case the sacrifice has to be considered a mistake. The queen may be out of play for a while during this extrication effort, giving Black the chance to gain in development, but that's unlikely to prove to have been sufficient compensation for the sacrifice. The recommended Bb5 move for White seems to be the quickest way to initiate the extrication.
It's a poorly played trap and definitely a blunder. White would still be up material even if the queen is lazily given up for pieces (see mainline.) However, white shouldn't be too impatient in freeing up the queen if it is decided that it should be kept (see sideline with checkmates.)
The best plan for white is probably to escape using minor pieces.
[FEN "rnbqk2r/pppp1pbp/4p1pn/4P3/2BP4/5Q2/PPP2PPP/RNB1K1NR b KQkq - 0 1"]
1...b6?? {Nf5 or Nc6 instead are playable} 2. Qxa8!+- Nc6 3.Nf3 {many other moves are playable} ( 3. Bg5?? Qxg5! 4. Qxc8+?! {Ne2 or Nd2 instead should be played} Ke7!-+ {the only move} 5. Qxc7 {Qb7 or Qa6 instead lead to the same checkmates} Qc1+!! (5... Bxe5?! 6. dxe5 {is not forced} Qc1+!) (5... Qxg2?? 6. Nd2!!+-) 6. Ke2 Nxd4+ 7. Kd3 Qxc2+ 8. Ke3 Nhf5+ 9. Kf4 {you can find two checkmate in threes from here})( 3. Bb5?! Nxd4 4. Qe4?! Nxb5 5. a4 {traps the knight}) O-O 4. O-O (4. Bb5) (4. Bg5) Qe7 5. Bb5 Ba6 6. Qxf8+ Qxf8 7. Bxa6
Black moves his/her knight to block the Queen from getting out. Then white is forced to work without a Queen or waste time trying to free her while black can make some aggressive moves without fear of the Queen being in the way. IMO it is a trap, at the expense of a rook but it buys time to make some pretty serious moves.
This rook sacrifice is a blunder. OK, you need to prove from a calculation standpoint also. Let's take the piece placement, and some basic common sense.
So in short b6 seems to be a misplayed move. You can even check this out with an engine.