Figure[White to move]

Here is a small study in how the threat of a discovery can influence other matters on the board. White has the makings of a discovered attack on the e-file. What could the rook on e1 attack if the bishop in front of it were moved? Just the pawn on e6. But notice that behind that pawn lies Black’s king. It’s another “if only” point: if only the pawn on e6 were gone, White would have a discovered check with Ba6+, winning the queen after Black moves his king. This means that the Black pawn on e6 in effect is pinned in place. White is free to play d4-d5 if he wishes; if Black captures with e6xd5, White replies with his discovered check. So if he is alert Black will instead reply with a move like Bd6 (preparing to castle) and allow White to play d5xe6 next move, planning to respond with f7xe6—but now Black’s position for castling is not quite so strong. Indeed, notice that Black’s position overall is rather poor. He is behind in development (too many pieces still on their original squares), and he has weak light-colored squares on his queenside (a6 and c6; they are “weak” in the sense that White can put pieces on them and Black can’t chase them away with pawns)—made worse by the fact that Black’s light-colored bishop, which he might have used to protect those squares, is off the board, while White’s still is available.

In any event, the general point of the study is just to see how the possibility of a discovered check in the background can influence other features of the game. The threat of it can paralyze those pieces that prevent its execution and so permit advances that would not otherwise be feasible. Here it ultimately causes Black to end up with an isolated pawn and bad castling position.