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Batteries and Discovered Lines

A battery is two line pieces on the same line, one behind the other. The front piece moves, and the back piece fires.

A queen and rook battery

The queen on a1 and the rook on a2 stand on the same file. The rook blocks the queen. When the rook moves, the queen will attack the rook on a8 along the a-file.

FEN: r3k3/8/8/8/8/8/R7/Q5K1 w - - 0 1

a b c d e f g h
8 r . . . k . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 . . . . . . . . 5
4 . . . . . . . . 4
3 . . . . . . . . 3
2 R . . . . . . . 2
1 Q . . . . . K . 1
  a b c d e f g h

A queen and bishop battery

The queen on d1 and the bishop on c2 stand on the same diagonal. The bishop moves to e4. The queen now attacks the queen on a4 along the opened diagonal.

FEN: k7/8/8/8/q7/8/2B5/3Q2K1 w - - 0 1

a b c d e f g h
8 k . . . . . . . 8
7 . . . . . . . . 7
6 . . . . . . . . 6
5 . . . . . . . . 5
4 q . . . . . . . 4
3 . . . . . . . . 3
2 . . B . . . . . 2
1 . . . Q . . K . 1
  a b c d e f g h

Key points

  • A battery places two pieces on one rank, file, or diagonal.
  • The front piece blocks the back piece.
  • The front piece moves away with a threat.
  • The back piece then attacks along the opened line.
  • Rook and queen batteries are common on open files.
  • Bishop and queen batteries are common on diagonals.
  • A battery turns one move into two threats.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Rust Playground

Exercise

White to move. Which rook move uncovers the queen's attack on the queen on d7?