Swallow's Tail Mate

The Swallowtail Mate (also called the Guéridon Mate) is a checkmate in which a queen checks the king from directly beside it, while the king's two escape squares behind it are blocked by its own pieces. Those two blockers, splayed out behind the king, make a V like a swallow's tail, which is where the name comes from. The queen covers the squares in front and to the sides; the defender's own pieces seal the back.

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Key pieceKey square

Why it is mate

The e5 king has eight neighboring squares, and each one is shut for a reason.

• d5, f5, d6, f6: the e6 queen covers all four. Standing one square in front of the king, it hits d5 and f5 along the diagonals and d6 and f6 along the sixth rank.
• e6: the queen's own square. The king could only get there by capturing it, and Kxe6 is illegal because the e8 rook defends the queen.
• e4: the king is checked down the e-file, so stepping to e4 keeps it on the checking line - still in check, and illegal.
• d4, f4: White does not attack these at all. Black's own pawns sit there, so the king cannot go.

The check cannot be answered either. Nothing can interpose on an adjacent check, and the queen cannot be taken. Four squares covered by the queen, the queen's own square guarded by the rook, two more filled by the defender itself, and the last one sealed by the check: all eight are accounted for.

The defender builds its own trap

The queen does the whole job in front of the king. The two squares behind - d4 and f4 - are shut by Black's own pawns, not by anything White did.

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Take the two pawns off and Black gains Kd4 and Kf4. No white piece has moved, yet the mate is gone. The Swallowtail only works when the king's own pieces wall in the two squares behind it, so finding it is mostly a matter of recognition: spot the king boxed in from behind, and a single protected queen finishes from the front.

Swallowtail vs Dovetail

The Swallowtail is easy to confuse with the Dovetail Mate, because both end with a protected queen right next to the king and two of the king's own pieces blocking its flight. The difference is the direction the queen checks from.

• Swallowtail: the queen is orthogonally next to the king (straight in front, along a file or rank). The two own-piece blockers then sit on the diagonal squares behind the king - the V of the tail.
• Dovetail: the queen is diagonally next to the king. The two blockers sit on the orthogonal squares beside and behind it - the notch of the dove's tail.

Same ingredients, mirrored geometry. Fix which way the queen attacks and the rest of the picture follows.

A real finish

Below is an actual position from our puzzle set. The king on f4 is walled in from behind by its own queen on e3 and its own pawn on g3, and the white queen mates from f5.

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The blockers here are a queen and a pawn rather than the tidy pair of pawns in the diagram, but the shape is the same: two of the king's own men on the rear diagonals, the white queen checking from straight in front.

On this site

Our puzzle database has 331 problems tagged as Swallowtail Mate (counted September 2026), and 54% of them sit below rating 1200. That may reflect how easily a king gets hemmed in by its own pieces at that level, though the tag counts alone do not show the cause. The rear blockers do not have to be pawns: as the example above shows, any of the defender's own pieces will do. Not one puzzle in our data carries both this tag and the Dovetail tag, so the two really are handled as separate patterns here.

Defending against it

• Keep a flight square behind the king. The trap needs both squares behind the king sealed; if even one is open, a single check is not mate.
• Watch a queen coming to an adjacent square. A protected queen landing right next to your king, with your own pieces behind it, is the whole pattern - break it by moving one of those pieces or by driving the queen off.
• Do not crowd your own king. Swallowtail mates almost always rely on the king being boxed in by its own force; give it room before the queen arrives.

References

• Lichess, puzzle theme Swallowtail mate (the source of this site's puzzle tags). https://lichess.org/training/themes
• Wikipedia, Checkmate pattern - Swallowtail (Guéridon) and Dovetail (Cozio) definitions. https://en.wikipedia.org/wiki/Checkmate_pattern
• Statistics produced by scripts/analyze-theme-stats.ts; the run is recorded in docs/data/swallowstailMate-stats.md.

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Related: Dovetail Mate · Back-Rank Mate · All tactics