The Swallow’s Tail Mate, also called the guéridon mate, is a queen checkmate where the king’s two rear escape squares are blocked by its own pieces.
A supported queen checks the king from the square directly in front of it. The king can’t go forward or sideways into the queen’s reach, and the two squares behind it are sealed by its own pieces, which spread out like a swallow’s forked tail.
It’s the cousin of the Dovetail Mate, with the king’s own pieces blocking the back squares rather than the diagonals. The French name, guéridon, likens the shape to a small three-legged table.
As always with these queen mates, the protection on the queen is what makes it work. When an enemy king has its retreat squares plugged by its own rooks or pawns, look for a defended queen to step in front.
Because the king’s two blocking pieces spread out behind it in a forked shape resembling a swallow’s tail; the French call it the guéridon, after a small round table.
Both use a supported queen against a self-blocked king. The Swallow’s Tail blocks the two rear squares; the Dovetail blocks the diagonal flight squares instead.
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