One of the methods of fast checkmate in chess game
TheLegal Trap orBlackburne Trap (also known asLegal Mate) is achess openingtrap, characterized by aqueen sacrifice followed by checkmate involving three minor pieces if Black accepts the sacrifice. The trap is named after the French playerSire de Legall.Joseph Henry Blackburne, a British master and one of the world's top five players in the latter part of the 19th century, set the trap on many occasions.
There are a number of ways the trap can arise; the one below shows a natural move sequence from asimultaneous exhibition in Paris.André Cheron, one of France's leading players, won with the trap as White against Jeanlose:
Blackpins theknight in the fight over the center. Strategically this is a sound idea, but there is a tactical flaw with the move.
5. h3
In this position 5.Nxe5? would beunsound. While the white queen still cannot be taken (5...Bxd1??) without succumbing to a checkmate in two moves, 5...Nxe5 would win the white knight (for the pawn) and protect the bishop on g4. Instead, with 5.h3, White "puts the question" to thebishop which must either retreat on the c8–h3 diagonal, capture the knight, be captured, or as in this game, move to an insecure square.
Black apparently maintains the pin, but this is a tactical mistake which loses at least apawn (see below). Relatively best is 5...Bxf3 (or 5...Bd7), surrendering thebishop pair and giving White a comfortable lead indevelopment, but maintainingmaterial equality. 5...Be6!? is also possible.
The tactical refutation. White seemingly ignores the pin and surrenders thequeen. Black's best course now is to play 6...Nxe5, where with 7.Qxh5 Nxc4 8.Qb5+ followed by 9.Qxc4, White remains a pawn ahead, but Black can at least play on. Instead, if Black takes the queen, White has checkmate in two moves:
The final position is apure mate, meaning that for each of the eight squares around the black king, there is exactly one reason the king cannot move there, and exactly one reason why the king cannot remain on its current square.[1]
The above version is cited in most publications, sometimes with the move 4... h6 instead of 4... g6. However, research suggests that themove order of the game had been altered retrospectively in order to remove a flaw in the original game.[5] Also the year 1750 is assumed to be wrong; it is more likely that the game was played in 1787, and that the original move order was:[2]
Here the combination is flawed, as with 5... Nxe5 Black could have gained a piece. It is reported that Legal disguised his trap with a psychological trick: he first touched the knight on f3 and then retreated his hand as if realizing only now that the knight was pinned. Then, after his opponent reminded him of thetouch-move rule, he played Nxe5, and the opponent grabbed the queen without thinking twice.[citation needed]
Sometimes the mate can be administered by a different piece. This game fromPetrov's Defence is very old (The line after 3.. Nc6?! 4.Nxc6 is now commonly referred to as the Stafford Gambit):
Position after 13...Ne7? after aRuy LopezBird's Defence opening from the gameShort–Kupreichik, Hastings 1981/82.[6] White gained a pawn with 14.Nxe5!; 14...Bxd1? is met with 15. Nd7+!, winning the queen and bishop (15...Kg8 16. Nxf6+) and damaging Black's pawn structure (16...gxf6 creates anisolated h-pawn anddoubled f-pawns), while taking the knight leaves the bishop hanging and allows White to activate their queen. Short went on to win the game.[7]
The Sea-Cadet mate
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A version of Legal's Mate occurred after 7...Ne5 in a casual game won byErnst Falkbeer at Vienna in 1847.[8] The game was arranged as a display of living chess in Act II ofDer Seekadet, an 1876 operetta by Genée and Zell:[9]
A mating pattern where a pinned knight moves, allowing the capture of the player's queen but leading to a checkmate with three minor pieces, occasionally occurs at lower levels of play, though masters would not normally fall for it. According to Bjerke (Spillet i mitt liv), the Legal Trap has ensnared countless unwary players. One author writes that "Blackburne sprang it several hundreds of times during his annual tours."[10]
