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"Pin" and "skewer" are fairly common terms in chess:

  • A pin is a situation where a piece cannot move without exposing a more valuable piece to attack. For example, the Ruy Lopez Opening features a black knight pinned (against the black king) by a white bishop after white's third move.

  • A skewer is when a piece is attacked and moving it would expose a less valuable piece to attack. An example would be a black rook attacking a white queen along a file with a white rook on the same file behind the queen.

However, I am unaware of a term applying to a similar situation in which the attacked piece is of equal value to the piece it is shielding, whether because they are two pieces of the same type (e.g. rooks) or the same value (bishop and knight, using "conventional" values of 3 pawns/points for both knights and bishops). Does such a term exist? If so, what is it? Or do we just use "pin" (or "skewer")?

The diagram shows an example with a white bishop attacking two black rooks along the same diagonal. (The black pawn is to rule out the possible responses Ra5 and Rb5, which distract from the point of the example.)

r7/1r2k3/8/1p1BK3/8/8/8/8 w - - 0 1
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    ... it's a fork – theonlygusti May 7 at 13:22
  • @theonlygusti it's not a fork – Darren H May 13 at 13:03
  • @DarrenH why?.. – theonlygusti May 13 at 13:55
  • @theonlygusti in a fork you are directly attacking two pieces, in this situation right now you are only attacking the rook on B7. You would only be attacking the rook on A8 if the rook on B7 moves out of the way or is taken by the bishop – Darren H May 13 at 15:14
  • @DarrenH I disagree. I've heard chess streamers call such a position a fork. I would also consider this position a fork, FEN 3kq3/3p1p1p/8/4R2b/3P4/4K3/8/8 b - - 0 1, even though white can only take the bishop if the queen moves — I think most people would consider these kinds of positions as fork. – theonlygusti May 13 at 16:44
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I'm not aware of any terms. Maybe it is helpful to think instead of the purpose of the move:

  • pin: preventing a piece from moving by threatening to attack a piece behind it
  • skewer: forcing a piece to move, in order to attack the piece behind it

So whether you call a situation with a knight in front of a bishop (or rook in front of a rook like in your board) a "skewer" or a "pin" depends perhaps on what the primary intention is.

In your board position, I would say that the A8 rook is skewered and the B7 rook is pinned.

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5

Simply call it a "double attack". The bishop is attacking the b7 rook directly and the a8 rook by x-ray. Of course pins & skewers involve an x-ray. But there are many double attacks ; some do & some do not involve an x-ray.

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    How about "x-ray double attack"? This is the most specific and applies best to the description of the poster. – Hauke Reddmann May 7 at 7:59
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    a double attack would be an attack on the same piece by two attackers. – Kami Kaze May 7 at 10:35
  • I'm familiar with the term 'x-ray' to more specifically refer to a piece that looks through another, following the line same direction of attack. ie: the white queen on b2 can attack a black piece on c3, but a black bishop on a1 can still attack the queen on c3 by x-ray. – Grade 'Eh' Bacon May 7 at 13:10
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    @KamiKaze no, that is not how the term "double attack" is commonly used in chess. In general, a double attack happens when a single move by a player creates two simultaneous threats against their opponent [from chess.com]. It need not involve "an attack on the same piece by two attackers". – Nihar Karve May 7 at 13:47

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