Legal's Trap
The famous queen offer wins a game or loses a piece depending on one square. See both versions on the board and know which reply to choose from either side.
Opening Moves
1. e4 e5 2. Nf3 Nc6 3. Bc4 d6 4. Nc3 Bg4
Decide from the position in front of you whether Nxe5 is a winning combination or a lost piece, and pick the right reply as Black instead of taking the queen.
After 1.e4 e5 2.Nf3 Nc6 3.Bc4 d6 4.Nc3 Bg4, the bishop on g4 pins the knight on f3 against the white queen. Almost every version of Legal's Trap begins by ignoring that pin.
The starting position for Legal's Trap. The bishop on g4 pins the f3-knight to the queen, and the bishop on c4 already eyes f7. — r2qkbnr/ppp2ppp/2np4/4p3/2B1P1b1/2N2N2/PPPP1PPP/R1BQK2R w KQkq - 2 5
Useful next actions:
The Mate That Gives The Trap Its Name
Move the f3-knight and the queen hangs. That is the whole offer. If Black accepts it, three white pieces finish the game in two moves: 5.h3 Bh5 6.Nxe5 Bxd1 7.Bxf7+ Ke7 8.Nd5#.
Reference works also list that finish as Legal's Mate, and call the pattern the Blackburne Trap after Joseph Henry Blackburne, a nineteenth-century British master who set it on many occasions.
Step through the sound version:
Ke7 is not one option among several. It is Black's only legal move, because the knight on e5 guards f7 and a bishop check from an adjacent square cannot be blocked.
The finished mate. The knight on d5 gives check and covers f6, the bishop covers e6 and e8, the knight on e5 covers d7, and Black's own queen and bishop seal d8 and f8. — r2q1bnr/ppp1kBpp/2np4/3NN3/4P3/7P/PPPP1PP1/R1BbK2R b KQ - 2 8
Read the last two escape squares again, because they explain when the pattern stops working. Black's king cannot run to d8 or f8 for the simple reason that Black's own queen and dark-squared bishop are still standing there. Against an opponent who has already played ...Qe7 or ...Be7, this mate does not exist.
From The Diagram Position, The Offer Loses A Piece
Now go back to the diagram at the top and try the trap immediately with 5.Nxe5.
Black has three captures: 5...Bxd1, 5...dxe5, and 5...Nxe5.
Only the third one works for Black.
After 5.Nxe5 Nxe5, the black knight does two jobs at once. It defends the bishop on g4 and attacks the bishop on c4, so White has no comfortable way to collect anything. — r2qkbnr/ppp2ppp/3p4/4n3/2B1P1b1/2N5/PPPP1PPP/R1BQK2R w KQkq - 0 6
White would like to answer 6.Qxg4, restoring material. The knight that just landed on e5 attacks g4, so 5.Nxe5 Nxe5 6.Qxg4 Nxg4 hands over a knight for a pawn and then a queen for a bishop.
White does not have to play that badly. 6.Be2 and 6.Bb5+ both keep the game going. They also leave White a clean piece down for one pawn, and Stockfish agrees that the position is already lost for White.
So the queen offer fails straight from the position at the top of this page. Black refutes it with an ordinary recapture.
h3 Is Not A Waiting Move
5.h3 looks like the slow move a strong player makes when nothing is happening. Here it is the whole trap. It is also Stockfish's first choice in the position, which is a useful coincidence rather than the reason to play it.
The reason is one square.
The same offer after 5.h3 Bh5 6.Nxe5. This time the queen's recapture square is h5, and a black knight arriving on e5 does not attack h5. — r2qkbnr/ppp2ppp/2np4/4N2b/2B1P3/2N4P/PPPP1PP1/R1BQK2R b KQkq - 0 6
A knight on e5 attacks g4. It does not attack h5. Pushing the bishop one square along the diagonal changes nothing about the pin and everything about the recapture, which is why 5...Bh5? is the move that walks into the real trap while 5...Bxf3 and 5...Be6 keep Black close to level.
This is also the honest version of a familiar piece of advice. Playing h3 to ask a bishop is usually described as a small prophylactic gesture, the kind covered in prophylaxis. In this position it is a concrete tactical preparation with a measurable result.
Correct Defence Still Costs Black A Pawn
Suppose Black sees through it after 6.Nxe5 and declines. The queen is safe on h5 now, so White collects the bishop and keeps a pawn: 6...Nxe5 7.Qxh5 Nxc4 8.Qb5+ c6 9.Qxc4.
6...dxe5 7.Qxh5 comes to much the same thing: White keeps the extra pawn and the easier game.
Worth stating plainly, because the mate gets all the attention: in the version that works, defending correctly does not win anything for Black. It avoids mate and concedes a pawn.
Four Conditions, One Test
Everything above reduces to four questions you can ask at the board before offering the queen.
| Condition | Why it matters |
|---|---|
| The knight is already on c3 | Nd5 is the mating move. Without a knight on c3, Nxe5 Bxd1 is a queen thrown away for a pawn, not a tactic. |
| No Black piece attacks the queen's recapture square | From g4 the recapture fails to ...Nxg4. From h5 it does not, because a knight on e5 does not reach h5. Count every black piece that hits the square, not only the one that recaptures: a knight on f6 attacks g4 and h5 both. |
| No Black piece or pawn guards d5 | Nd5 has to be mate, not check. A knight on f6 or e7, or a pawn on c6 or e6, covers d5 and simply takes the knight. |
| Black's queen and dark-squared bishop are still at home | They are the pieces that block d8 and f8 for their own king. |
The second row is why the trap turns up in the Philidor Defence, where Black plays ...d6 before developing the queen's knight. After Nxe5, the pawn on d6 is the only recapture; after ...dxe5, no black knight has landed on e5 to hit g4. That is not the same as g4 being safe, and the Philidor is the clearest place to see why the questions have to be asked one at a time.
After 1.e4 e5 2.Nf3 d6 3.Bc4 Nf6 4.Nc3 Bg4, the knight on f6 changes the position completely:
The f6-knight touches all three squares that matter: g4, h5, and d5. That is why the usual Legal's Trap pattern no longer works. — rn1qkb1r/ppp2ppp/3p1n2/4p3/2B1P1b1/2N2N2/PPPP1PPP/R1BQK2R w KQkq - 4 5
That one knight breaks the idea in three different ways. If White captures on e5 and then takes the bishop, the knight can take on g4. If White tries to improve the offer with h3 and Qxh5, the same knight can take on h5. And if Black accepts the queen, Nd5+ is only check, not mate, because the f6 knight can capture on d5. Two of the four conditions fail at once, from one ordinary developing move.
A pawn on c6 breaks the trap in a different way:
After 4...c6, the g4 bishop still pins the queen, but the c6-pawn guards d5. That one pawn turns Nd5 from mate into only a check. — rn1qkbnr/pp3ppp/2pp4/4p3/2B1P1b1/2N2N2/PPPP1PPP/R1BQK2R w KQkq - 0 5
Here Black should take the queen. After 7...cxd5, the mating knight disappears and Nd5+ is only a check. Playing h3 first changes nothing, because the failed square is still d5.
That is also the general lesson worth keeping. A pin is absolute only when the king stands behind it. Everything else is a question of price, and the price of breaking this pin is a queen. It is worth paying exactly when a mate follows and never otherwise.
Where Legal's Name Comes From
The historic game, and why the move order matters
The pattern is named for Legall de Kermeur, an eighteenth-century French player who was also Philidor's teacher. The miniature usually printed under his name runs 1.e4 e5 2.Bc4 d6 3.Nf3 Bg4 4.Nc3 g6 5.Nxe5 Bxd1 6.Bxf7+ Ke7 7.Nd5#, reaching the same mating net shown earlier on this page.
Step through the printed score:
The old story is not a clean modern game record. Sources give different dates, and some accounts say the score was tidied from a rook-odds game into the neat version players learn today. That uncertainty is less important than the move order. In the printed mate, Black's b8-knight never reaches c6, so it cannot recapture on e5 and defend the bishop on g4. If Black has already played ...Nc6, the same queen offer usually fails to ...Nxe5.
At The Board
For White, the trap is not Nxe5 by itself. First make Black move the pinned bishop with h3. If Black answers ...Bh5, the queen offer can work because the bishop is no longer sitting on a square that a knight on e5 attacks. If Black answers ...Bxf3 or ...Be6, the tactic is gone; play the position normally instead of forcing the pattern.
For Black, the rule is just as concrete: before taking the queen, check d5. If White can answer with Bxf7+ and Nd5#, the queen is poisoned. If one of your pieces or pawns controls d5, Nd5 is only a check, and the queen capture may be safe. In the top diagram, Black has an even simpler answer: ...Nxe5 wins the knight and protects the bishop on g4 at the same time.
Useful next steps:
- Practice Legal's Trap
- Compare Black's fifth-move choices
- Build a real opening around Bc4
- Study the other attack on f7
- Make a pattern stick
Keep studying this opening
- Practice Legal's Trap: Train the position against realistic replies.
- Explore the Legal's Trap position: Review the move tree from the opening tabiya.