Figure[Black to move]

Now a glance at our current topic from a defensive standpoint. Black needs to move his queen to avoid b4xQ, so he considers Qxa3, which seems to win a loose pawn. But before making a venture like this, especially into enemy territory, look for any tactical ideas your opponent may have in place. Where does White have the kernel of a discovery? The sight of his knight masking his rook on the third rank is cause for alarm; if Black plays Qxa3, White can attack Black’s king and queen at the same time with the crushing horizontal discovery Nd5+.