Check

An attack by a piece or a pawn on the enemy king. The player whose king is in check must, on the reply move:

• move the king to a square that no enemy piece attacks;
• or capture the enemy piece that threatens the king;
• or move one of their own pieces to a square between the king and the piece attacking it.

The last defense is impossible when the check comes from a knight.

Discovered and double check

The defenses listed above work against an ordinary check and against a discovered check — in a discovered check the piece that moves opens the line of another piece, and the king comes under fire from that piece.

Against a double check, though — when the piece that opens the line of another piece attacking the king gives check itself as well — only one defense is left, moving the king away, for example:

Boards can be stepped through with the mouse wheel, a swipe, or the arrow keys — not just the buttons below them. Interactive boards

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1. 1.
2. Any rook move opens the bishop's line and gives discovered check
3. Double check
4. Double check

Perpetual check

If one side gives a run of checks one after another and the enemy king cannot hide from them, the result is perpetual check. The game is then counted as a draw.