Légal Trap

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The Légal Trap or Blackburne Trap (also known as Légal Pseudo-Sacrifice and Légal Mate) is a chess opening trap, characterized by a queen sacrifice followed by checkmate with minor pieces if Black accepts the sacrifice. The trap is named after the French player Sire de Légal (1702–1792). Joseph Henry Blackburne (1841–1924), 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.


Natural move sequence[edit]

There are a number of ways the trap can arise, the one below shows a natural move sequence from a simultaneous exhibition in Paris. André Cheron, one of France's leading players, won with the trap as White against Jeanlose:

1. e4 e5 2. Nf3 Nc6 3. Bc4 d6

The Semi-Italian Opening.

4. Nc3 Bg4?!

Black pins the knight 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 be unsound. While the white queen still cannot be taken (5...Bxd1??) without succumbing to a checkmate in two moves, 5...Nxe5 would win a knight (for the pawn). Instead, with 5.h3, White "puts the question" to the bishop which must either retreat on the c8–h3 diagonal, capture the knight, be captured, or as in this game, move to an insecure square.

5... Bh5? (see diagram)

a b c d e f g h
8
Chessboard480.svg
a8 black rook
d8 black queen
e8 black king
f8 black bishop
g8 black knight
h8 black rook
a7 black pawn
b7 black pawn
c7 black pawn
f7 black pawn
g7 black pawn
h7 black pawn
c6 black knight
d6 black pawn
e5 black pawn
h5 black bishop
c4 white bishop
e4 white pawn
c3 white knight
f3 white knight
h3 white pawn
a2 white pawn
b2 white pawn
c2 white pawn
d2 white pawn
f2 white pawn
g2 white pawn
a1 white rook
c1 white bishop
d1 white queen
e1 white king
h1 white rook
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
After 5...Bh5?
a b c d e f g h
8
Chessboard480.svg
a8 black rook
d8 black queen
f8 black bishop
g8 black knight
h8 black rook
a7 black pawn
b7 black pawn
c7 black pawn
e7 black king
f7 white bishop
g7 black pawn
h7 black pawn
c6 black knight
d6 black pawn
d5 white knight
e5 white knight
e4 white pawn
h3 white pawn
a2 white pawn
b2 white pawn
c2 white pawn
d2 white pawn
f2 white pawn
g2 white pawn
a1 white rook
c1 white bishop
d1 black bishop
e1 white king
h1 white rook
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
Légal's Mate: 8.Nd5#
Black apparently maintains the pin, but this is a tactical blunder which loses at least a pawn (see below). Relatively best is 5...Bxf3, surrendering the bishop pair and giving White a comfortable lead in development, but maintaining material equality. 5...Be6!? is also possible.

6. Nxe5!

The tactical refutation. White seemingly ignores the pin and surrenders the queen. 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:

6... Bxd1?? 7. Bxf7+ Ke7 8. Nd5#

The final position (see diagram) is a pure mate, meaning that for each of the eight squares around the black king, there is exactly one reason the king cannot move there.[1]

Légal versus Saint Brie[edit]

The original game featured Légal playing at rook odds (without Ra1)[2] against Saint Brie in Paris 1750:

1. e4 e5 2. Nf3 d6 3. Bc4 Bg4?! 4. Nc3 g6? 5. Nxe5 Bxd1?? 6. Bxf7+ Ke7 7. Nd5# 1–0[3][4]

Note: The above move order is found in most publications; however, research published at ChessBase[5] suggests that the move order has been altered retrospectively in order to remove a flaw in the original game. 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:

1. e4 e5 2. Bc4 d6 3. Nf3 Nc6 4. Nc3 Bg4 5. Nxe5? Bxd1?? 6. Bxf7+ Ke7 7. Nd5# 1–0

Here the combination is flawed, as with 5... Nxe5 Black could have gained a piece. It is reported that Légal 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 the touch-move rule, he played Nxe5, and the opponent grabbed the queen without thinking twice.[citation needed]

Other variations[edit]

Black springs Légal's Trap on White
a b c d e f g h
8
Chessboard480.svg
a8 black rook
d8 white bishop
e8 black king
h8 black rook
a7 black pawn
b7 black pawn
c7 black pawn
f7 black pawn
g7 black pawn
h7 black pawn
c6 black pawn
e4 black knight
g4 black bishop
d3 white pawn
a2 white pawn
b2 white pawn
c2 white pawn
e2 white king
f2 black bishop
g2 white pawn
h2 white pawn
a1 white rook
b1 white knight
d1 white queen
f1 white bishop
h1 white rook
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
Sometimes the mate can be administered by a different piece. This game from the Petrov's Defence is very old:
1.e4 e5 2.Nf3 Nf6 3.Nxe5 Nc6?! 4.Nxc6 dxc6 5.d3 Bc5 6.Bg5? Nxe4 7.Bxd8?? Bxf2+ 8.Ke2 Bg4# 0–1
The Trap in a modern middlegame
a b c d e f g h
8
Chessboard480.svg
a8 black rook
f8 black king
h8 black rook
a7 black pawn
c7 black pawn
e7 black knight
f7 black pawn
g7 black pawn
h7 black pawn
b6 black bishop
d6 black pawn
f6 black queen
e5 black pawn
a4 white bishop
e4 white pawn
g4 black bishop
c3 white pawn
d3 white pawn
e3 white bishop
f3 white knight
b2 white pawn
f2 white pawn
g2 white pawn
h2 white pawn
a1 white rook
d1 white queen
e1 white king
h1 white rook
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
Position after 13...Nc6–e7? after a Ruy Lopez Bird's Defence opening from the game Short vs. Kupreichik, Hastings 1981/82. White gained a pawn by 14.Nxe5 and subsequently won.[6]
The "Sea-Cadet" Mate
a b c d e f g h
8
Chessboard480.svg
a8 black rook
d8 black queen
e8 black king
f8 black bishop
g8 black knight
h8 black rook
a7 black pawn
b7 black pawn
c7 black pawn
f7 black pawn
g7 black pawn
h7 black pawn
d6 black pawn
e5 black knight
c4 white bishop
e4 white pawn
g4 black bishop
c3 white knight
f3 white knight
a2 white pawn
b2 white pawn
f2 white pawn
g2 white pawn
h2 white pawn
a1 white rook
c1 white bishop
d1 white queen
f1 white rook
g1 white king
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
A version of Légal's Mate occurred after 7...Ne5 in a casual game won by Falkbeer at Vienna in 1847. The game was arranged as a display of living chess in Act II of Der Seekadet, an 1876 operetta by Genée and Zell:[7]
1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.c3 (the Göring Gambit) dxc3 5.Nxc3 d6 6.Bc4 Bg4 7.0-0 Ne5 8.Nxe5 Bxd1 9.Bxf7+ Ke7 10.Nd5# 1–0

Considerations[edit]

This kind of mate, where an apparently pinned knight moves anyway, allowing capture of the queen, but leading to a checkmate with 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 Légal Trap has ensnared countless unwary players. One author writes that "Blackburne sprang it several hundreds of times during his annual tours."[8]

In general, making a "trap" by luring a bishop into a queen capture is not strictly necessary. Any game featuring an advanced knight and Bxf7+ (or ...Bxf2+) followed by mate with minor pieces would be considered a Légal Mate. The mate succeeds because the square of the advanced knight is unguarded, and the enemy king is blocked by several of its own pieces.

See also[edit]

References[edit]

  1. ^ This version of the Légal Trap was presented in Andre Bjerke (1975). Spillet i mitt liv (in Norwegian). ISBN 82-03-07968-7. 
  2. ^ George Walker, A Selection of Games at Chess (London: Gilbert and Rivington, 1835), p. 91.
  3. ^ Chessgames.com (http://www.chessgames.com/perl/chessgame?gid=1250654)
  4. ^ Georges Renaud & Victor Kahn The Art of Checkmate; Dover 1962
  5. ^ René Gralla, Das Seekadetten-Matt: Original und Fälschung (http://de.chessbase.com/post/das-seekadetten-matt-original-und-flschung)
  6. ^ Hooper, Whyld (1987), p. 182
  7. ^ Hooper, Whyld (1987), p. 302
  8. ^ Francis J. Wellmuth The Golden Treasury of Chess; Chess Review 1943, p. 147.

Bibliography

External links[edit]