Moving a piece out of the way to check

Question

I was recently told that you may not move a piece out of the way of a second piece to allow the second piece to put the other player in check.

For example,

• I have my queen and rook lined up on a diagonal with my opponent's king.
• I move my rook, opening the path for my queen to their king putting it in check.

According to my opponent, you aren't allowed to do this. You have to actively move the queen into a check position.

Is this a standard rule?

Answer 1

You can move your other piece to make your queen attack the king in a normal position such as:

4r3/8/8/2QB1k2/p5q1/3K4/8/8 w - - 0 1

1.Bf3+**[Discovered-Check]
(1.Be4+**[Double-check])

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But you are forbidden to do so if the piece you move will put your own king in check, such as:

3r4/8/8/2QB1k2/p5q1/3K4/8/8 w - - 0 1

1.Bf3**[illegal-move] 

Here both Be4 and Bf3 are illegal because the rook on d8 will be attacking your King.

So to conclude, there is no standard rule avoiding you to play discovered check except when the move puts your own king in check.

Answer 2

As mentioned by others, this move is perfectly legal (unless it puts your own king in check) and is called discovered check or more generally discovered attack (if the attacked piece is not the king).

This is usually a deadly tactic because the piece moved effectively gets to move twice while the opponent has to deal with the check from the other piece. This allows you to:

1. The moved piece can move to a square where it attacks a stronger piece which it will capture in the next move. (Bh7+ in the example below). The attacked piece cannot escape because the king is in check.
2. The moved piece can capture anything directly without being recaptured. (Bxc6+ in the example below).

Take a look at the following example:

[FEN "6q1/1p6/2p5/4k3/3pB3/6P1/5P1P/4R1K1 w - - 0 1"]

1. Bh7+ {Black has to deal with the check and cannot capture this bishop with the queen} (1. Bxc6+ {Even though this pawn is protected by the pawn on b7, black has to deal with the check and cannot capture the bishop} Kd6 2. Bxb7 {White won two pawns}) Kd6 2. Bxg8

Answer 3

For USCF rules, there is no such rule as long as the piece you are moving does not expose your king to check in the process.

Answer 4

It's perfectly accurate to say that there is no such rule in the Laws of Chess. Also, if your queen, your rook and his king are in a row his king is already in check, so his last move must have been illegal.