Double-check mate by discovery — Chess Library

One bishop move uncovers a rook check and gives a second check itself. Double check leaves the defender only king moves—and here none exist.

Lesson

White to move. Main line: 1. Bb5#

Bb5 delivers two checks at once. The bishop attacks e8 along b5–c6–d7–e8, while moving away from e2 opens the rook’s e-file. Because two pieces are checking, Black cannot solve the position by capturing or blocking only one attacker.

A king must move when it is double-checked. In this position d8 and f8 contain black rooks, f7 contains a black pawn, d7 is covered by the white knight on b6, and e7 is controlled by the rook. Every adjacent square is sealed.

When a line piece sits behind one of your pieces, consider every move that uncovers it with tempo. A discovered check is forcing; a double check is even more restrictive because it reduces the calculation tree to king moves alone.