Quick answer
X-Ray Attack is a tactical idea: two aligned attackers on the king file. Work from the first evidence position for X-Ray Attack, and begin by testing Qb4.
Begin from Qb4 in 8/5k2/4p3/8/8/2Q5/4R3/6K1 w - - 0 3. Start with the forcing geometry: checks, captures, threats, defenders and flight squares around the target. The evidence answer is: X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Qb4.
In the X-Ray Attack example, notice: side White; pieces Black king f7, Black pawn e6, White queen c3, White rook e2, White king g1; legal first moves Qb4, Qa5, Qc4, Qc5, Qc6, Qc7+, Qc8, Qd4. Read those squares as a snapshot of this single board, not as a standing rule you can copy into every game.
The tactical trigger
The first evidence board tests two aligned attackers on the king file; the second board tests two aligned attackers on the king file. Construction note: A = direct FEN setup; B = direct FEN setup. Rebuild each board before comparing labels. Hub vocabulary: Chess Wiki · Tactics hub. Then compare Candidate Moves with Cross Pin, X Ray Defense, Battery around the mating net's boundary.
The two inventories make the distinction concrete. A contains side White; pieces Black king f7, Black pawn e6, White queen c3, White rook e2, White king g1; legal first moves Qb4, Qa5, Qc4, Qc5, Qc6, Qc7+, Qc8, Qd4; B contains side Black; pieces Black king d7, Black pawn e7, White rook e6, White queen g2, White king g1; legal first moves Kc8, Kd8, Ke8, Kxe6, Kc7. Compare the side to move before comparing the labels in the context of the exchange that removes a guard.
Topic dossier for this page and board pair r1:8 | r2:5k2 | r3:4p3 | r4:8 | r5:8 | r6:2Q5 | r7:4R3 | r8:6K1 / r1:8 | r2:3kp3 | r3:4R3 | r4:8 | r5:8 | r6:8 | r7:6Q1 | r8:6K1: start with the mating net's boundary; then test the exchange that removes a guard; keep a counter-check that changes the calculation separate from a deflection from the critical square; use the final simplification as the transfer check; and reserve the last safe flight square for the exception.
Calculation order
On the first board, calculate Qb4 after Qb4 and write down the opponent's best reply around the mating net's boundary. On the second board, calculate Kc8 after Kc8 and check the exchange that removes a guard. Calculate the most forcing move first, then test the opponent's best capture, interposition or counter-check before naming the motif. In this case the useful condition is the last safe flight square.
Key claim: X-Ray Attack is illustrated here by two aligned attackers on the king file; the first concrete test is Qb4. The board anchor is 8/5k2/4p3/8/8/2Q5/4R3/6K1; the example is intentionally narrower than the topic label and should not be generalised without checking the surrounding position..
Practical boundary: To answer “How can a player recognize x-ray attack, calculate the winning idea, and test the defender's best resource?”, compare the recorded setup with Kc8 and the opponent's reply. The decision is useful only when the stated condition survives that concrete test on board 8/3kp3/4R3/8/8/8/6Q1/6K1. The evidence records Illustrative evidence for the stated mechanism; it is not a claim that the candidate move is forced or best in every position and the second board signature r1:8 | r2:3kp3 | r3:4R3 | r4:8 | r5:8 | r6:8 | r7:6Q1 | r8:6K1. The false-positive test is whether a counter-check that changes the calculation appears without a deflection from the critical square, so the conclusion is useful only when the stated condition survives that concrete test.
Evidence positions
example-1: two aligned attackers on the king file
Show answer
X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Qb4.
Why this position is here: X-Ray Attack is represented by two aligned attackers on the king file. This is a direct FEN setup with board anchor 8/5k2/4p3/8/8/2Q5/4R3/6K1; no opening history is inferred from the diagram.
FEN: 8/5k2/4p3/8/8/2Q5/4R3/6K1 w - - 0 3
Question: What is the first concrete decision in this x-ray attack position?
Answer cue: X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Qb4. The first candidate to test is Qb4. Replay Qb4 on board anchor 8/5k2/4p3/8/8/2Q5/4R3/6K1 and write down what changes after it.
Evidence boundary: Illustrative evidence for the stated mechanism; it is not a claim that the candidate move is forced or best in every position.
example-2: two aligned attackers on the king file
Show answer
X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Kc8.
Why this position is here: X-Ray Attack is represented by two aligned attackers on the king file. This is a direct FEN setup with board anchor 8/3kp3/4R3/8/8/8/6Q1/6K1; no opening history is inferred from the diagram.
FEN: 8/3kp3/4R3/8/8/8/6Q1/6K1 b - - 3 2
Question: What is the first concrete decision in this x-ray attack position?
Answer cue: X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Kc8. The first candidate to test is Kc8. Replay Kc8 on board anchor 8/3kp3/4R3/8/8/8/6Q1/6K1 and write down what changes after it.
Evidence boundary: Illustrative evidence for the stated mechanism; it is not a claim that the candidate move is forced or best in every position.
example-3: two aligned attackers on the king file
Show answer
X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Kc8.
Why this position is here: X-Ray Attack is represented by two aligned attackers on the king file. This is a direct FEN setup with board anchor 8/3kp3/7R/8/8/6Q1/8/6K1; no opening history is inferred from the diagram.
FEN: 8/3kp3/7R/8/8/6Q1/8/6K1 b - - 3 2
Question: What is the first concrete decision in this x-ray attack position?
Answer cue: X-Ray Attack: preserve the alignment and calculate the defensive interposition before trading the front piece. Candidate line: Kc8. The first candidate to test is Kc8. Replay Kc8 on board anchor 8/3kp3/7R/8/8/6Q1/8/6K1 and write down what changes after it.
Evidence boundary: Illustrative evidence for the stated mechanism; it is not a claim that the candidate move is forced or best in every position.
Reading the line
Read the first example (id example-1) as a complete record: continuation Qb4, source fide-laws. This is a direct FEN setup with board anchor 8/5k2/4p3/8/8/2Q5/4R3/6K1; no opening history is inferred from the diagram. If A does not expose two aligned attackers on the king file, correct the evidence before relying on the prose.
Read the second example (id example-2) separately: continuation Kc8, source fide-laws. Its feature is two aligned attackers on the king file; inventory side Black; pieces Black king d7, Black pawn e7, White rook e6, White queen g2, White king g1; legal first moves Kc8, Kd8, Ke8, Kxe6, Kc7. Compare what changes between Qb4 and Kc8.
The defensive resource
The main mistake to avoid with X-Ray Attack is spotting a familiar motif but failing to test the defender's strongest legal resource. In A, the missing condition must be located in r1:8 | r2:5k2 | r3:4p3 | r4:8 | r5:8 | r6:2Q5 | r7:4R3 | r8:6K1 after Qb4; in B, test it against r1:8 | r2:3kp3 | r3:4R3 | r4:8 | r5:8 | r6:8 | r7:6Q1 | r8:6K1 after Kc8.
For X-Ray Attack, the first board's evidence boundary (after Qb4) is Illustrative evidence for the stated mechanism; it is not a claim that the candidate move is forced or best in every position. The second board's evidence boundary for X-Ray Attack is Illustrative evidence for the stated mechanism; it is not a claim that the candidate move is forced or best in every position. If a trusted source or careful calculation changes the conclusion around the final simplification, update both the evidence record and this article.
Practice from a real game
cover the answer, list checks and captures, and record the defender or escape square that decides whether the idea works. Start with A's side to move and r1:8 | r2:5k2 | r3:4p3 | r4:8 | r5:8 | r6:2Q5 | r7:4R3 | r8:6K1; record two candidates, the reply to Qb4 and the correction. Repeat with B's side to move and r1:8 | r2:3kp3 | r3:4R3 | r4:8 | r5:8 | r6:8 | r7:6Q1 | r8:6K1; the changed board tests transfer rather than diagram memory.
After the drill, compare your notes with Cross Pin, X Ray Defense, Battery through a deflection from the critical square. Keep A's rejected alternative beside B's chosen line Kc8; this shows whether the conclusion survived a new board signature.
Sources and scope
Sources for X-Ray Attack: 1chess.online editorial scope, FIDE Laws of Chess. Source ids are original-analysis, fide-laws. Primary evidence hook: fide-laws. Comparisons and practice notes are editorial. Evidence revision: 2026-08-remediation-r2.
Scope note for board pair r1:8 | r2:5k2 | r3:4p3 | r4:8 | r5:8 | r6:2Q5 | r7:4R3 | r8:6K1 / r1:8 | r2:3kp3 | r3:4R3 | r4:8 | r5:8 | r6:8 | r7:6Q1 | r8:6K1: this page does not claim that Qb4 is an engine principal variation, that an exact endgame result is verified when the evidence says it is not, or that a tool output replaces human calculation. The conclusion is limited to the recorded boundary and the exception a counter-check that changes the calculation.