X-Rays in Chess: attacking through an enemy piece

X-rays are one of those tactics that make you see the board in a completely new way. Instead of looking at what’s in front of your pieces, you start seeing what’s behind. It’s like having vision through walls. And once you learn to spot them, you find threats that used to be completely invisible to you.

The concept: attacking through a piece

What exactly are X-rays? Imagine your rook is on the e-file and on that same file there’s an enemy piece (say, a bishop) with the enemy king behind it. Your rook doesn’t attack the king directly because the bishop is in the way. But if that bishop moves or is captured, the king becomes exposed to your rook’s attack.

That invisible pressure, that latent threat that exists through an intermediate piece, is what we call X-rays. The long-range piece “sees” what’s behind the obstacle, just like real X-rays see through matter.

X-rays vs. pin vs. skewer

Let’s clear up something that causes a lot of confusion. X-rays are related to the pin and the skewer, but they’re not the same thing:

• Pin: your piece attacks an enemy piece that has a more valuable piece (or the king) behind it. The piece in the middle can’t move without exposing the one behind it.
• Skewer: your piece attacks a valuable piece that, when it moves, exposes a less valuable piece behind it. It’s like an inverted pin.
• X-rays: the broader concept. Any pressure exerted through an intermediate piece. The intermediate piece can be yours or the opponent’s. It doesn’t necessarily immobilize anything; the threat simply exists if the obstacle disappears.

X-rays are the principle; the pin and the skewer are specific applications of that principle.

Pieces that execute X-rays

Only long-range pieces can create X-ray threats:

• The queen: the queen of X-rays. It attacks along ranks, files, and diagonals. It can exert pressure through pieces in any direction.
• The rook: X-rays along ranks and files. Very common in open positions where files are clear except for one intermediate piece.
• The bishop: X-rays along diagonals. The long diagonals are especially dangerous because they cross the entire board.

The knight and the pawn can’t do X-rays. Their movement doesn’t follow continuous lines, so they don’t “see” through anything.

How to take advantage of X-rays

X-rays help you detect hidden threats and create combinations. Let’s go over the practical applications:

1. Defending with X-rays

Your rook is on e1 and your opponent threatens a piece on e4. Between your rook and that piece there are other pieces. But if the line clears (through trades or moves), your rook defends e4. X-rays let you count that rook as a potential defender, even though it’s not directly defending right now.

2. Attacking with X-rays

Your bishop is on a1 and on the a1-h8 diagonal there’s an enemy pawn on d4 and behind it the enemy queen on f6. If the pawn on d4 advances or is captured, your bishop attacks the queen. You can force that advance or capture to materialize the threat.

3. Combinations based on X-rays

Many tactical combinations work because a piece exerts X-ray pressure that isn’t obvious at first glance. A sacrifice that clears a line can activate an X-ray attack that turns out to be decisive.

For example: you sacrifice a piece on e4 to eliminate the pawn blocking the diagonal. Your bishop on b1, which seemed inactive, suddenly attacks through the cleared diagonal and threatens checkmate.

How to spot X-rays in your position

Here’s a method that always works:

1. Trace the lines of your long-range pieces. For every queen, rook, and bishop, follow their attacking lines to the edge of the board, ignoring the pieces in between.

2. What’s at the end of those lines? If there’s a valuable opponent piece at the end (their king, their queen, a rook), you have a potential X-ray.

3. Can the obstacle be removed? If the intermediate piece can be captured, traded, or forced to move, your X-ray threat becomes a real threat.

4. Calculate the sequence. How many moves do you need to clear the line? Can the opponent prevent it? If the sequence works, you’ve found a combination.

The most common mistake

The most frequent mistake with X-rays is not seeing them. Most players only evaluate direct threats: what the pieces visibly attack. But X-ray threats are there, waiting for the moment to materialize.

The other mistake is forgetting that the opponent also has X-rays. Before moving a piece that’s blocking a line, ask yourself: by moving this piece, am I exposing something to an opponent X-ray attack? If the answer is yes, look for another move.

Once you master X-rays, you’ll see the board in three dimensions: not just what’s there, but what could be there if the pieces moved.

Related tactics: The Pin · The Skewer · The Seventh Rank