X-Ray Attack, Definition 3, A Defensive X-Ray Attack:
Part of the Chess Tactics Guide

Chess Tactics Guide
X-Ray Attack
[Definition 3: A Defensive X-Ray Attack]

Definition 3: When Defending a friendly piece through one or more enemy pieces. You may be inviting the enemy piece to capture your attacking piece, but it could be part of an overall sacrificial plan, of yours, that secures the advantage in material, and/or positioning on the board.

In this example, the defensive X-Ray by Black's Qd1 helps to defend Rd7, through the enemy Rd4.

Move 1, White's Queen strides left, onto a3, to protect her Pawn; Black's Rook, on the f-file, comes across to d8, forming a Battery on the d-file.

Agreed ... Black's Rook, on d7, could have easily captured White's d4 Rook ... ... but that would have ruined this 3rd Definition of the X-Ray Attack.

Move 2, White's Rook, on the f-file, slides left, onto d1, to support his fellow Rook; Black's Queen leaves the Pawn and nips across to h5.

Move 3, White's Queen drops down onto a1, to protect her Rook; Black's Queen then allows herself to be sacrificed, but in the process, captures (x) Black's Rook, on d1 and putting White's King in "Check" (+).

Not only is this a three-way Fork Attack, on White's King, Queen and Rook; it's also an X-Ray! Black's Queen, in this Definition 3 example, is Defending her friendly Piece - the d7 Rook - through an enemy Piece - White's Rook.

That single, sacrificial, X-Ray + Fork Attack maneuver, ends up being the catalyst that, in this scenario, Wins Black the game ...

Move 4, White's Rook captures (x) Black's Queen, on d1; Black's Rook captures (x) White's Rook, on d1.

(Can you see what's coming!?)

Move 5, White's Queen captures (x) Black's Rook, on d1; Black's Rook swoops down to capture (x) White's Queen, on d1 and lands a Back-Rank "Checkmate" (#), against White's helpless King.

Game Over, Black Wins (0-1).

And that neatly rounds-off this 3rd Definition X-Ray Attack