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BROWN BELT - DOUBLE-CHECKMATING
By this point in this parent tutorial you may have picked up on a theme: the Tactixbands get darker as the year goes on, and the tactics get harder, which means the darker the wristband the more prestige each carries. The Brown Belt is the most difficult and rare tactic of them all: the double checkmate!
Is a double checkmate even possible, or legal? Yep. Fun fact: even a triple checkmate is possible, but it requires the rare situation in which illegal moves have existed on a chess board for three moves and neither player had been aware of the illegality. In that case, a double checkmate in combination with a check no one had noticed before could theoretically result in the mythical triple checkmate. Oooo.
A double checkmate is the situation on the chessboard when one piece moves and checks the opponent's king, and a piece behind the moving piece also checks, and no move stops both checks. This situation is known as a double checkmate and it earns an immediate Brown Belt!
Here is a classic example:
Note that when the knight moves to B6 to check, the rook behind also checks. This is a double checkmate! Here is another example. Note that no move for black stops both checks.
An interesting and unique element of a double checkmate is that two of the usual three ways to stop a check--capturing the attacker or interposing and blocking the check--are impossible with a double check. Only moving the king so that both checks are avoided can stop a double check. And when nothing stops both checks, that is a double checkmate. In the situation below, note black can easily capture either of the checking pieces, but no move captures both, and so this is the rare double checkmate. Do you see the double checkmating move below for white?
Yes! It is for the rook to drop down to the green B8 square. When that happens, the bishop on the yellow A1 square also checks, and although black can capture either piece easily, and can block either check easily by interposing (getting between the checking piece and the king), no move will stop both. Double checkmate!
That's how to double checkmate!