Double Check is when two pieces simultaneously deliver a check to the opposing king. It is one of the most powerful forms of attack in chess.

Why Is It So Powerful?

• In a double check, interposing a piece is not possible (there are attacks from two directions).
• The attacking pieces cannot be captured (both cannot be captured at once).
• The king's only option is to move.

For these reasons, a double check often leads to unfavorable outcomes and is frequently used in checkmate combinations.