Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nd4

Black violates an opening principle by again moving his knight. Black hopes to tempt White into taking the now unprotected e5 pawn.

4. Nxe5? falls into Blacks trap. After 4...Qg5, forking White's knight the g2 pawn, White is in dire trouble. If White attempts to save the knight, 5. Nxf7?? Qxg2 then White has to give up the rook instead. If they try to hold onto their rook, then they must give up their queen or get mated. 6. Rf1?? Qxe4+ 7. Qe2 (7. Be2?? Nf3#) 7...Nxe2-+. 5. Bxf2+⩱ is the only way to stay in the game.

The Blackburne Shilling is a one-trick pony: as long as White avoids 4. Nxe5 they are comfortably ahead. For this reason Black players are supposed to exclaim, "Oh my God!" to sell the illusion that they have blundered a pawn.

Black's knight is misplaced and they are falling behind in development so White has lots of good options. White can simply decline the gambit with 4. O-O or kick Black's knight with 4. c3 (both of these usually induce 4...Nxf3 5. Qxf3). The most critical line is 4. Nxd4.

4. Nxd4 exd4 trades knights and dislodges Black's pawn from e5. This opens up a number of tactical opportunities for White. After 4...exd4, White has an idea of playing e5 themself, e.g. 4..exd5 5. O-O Nf6 6. Re1 Bc5? 7. e5! Ng8 (only safe square for the knight). Another idea is that Qh5 can attack f7 while forking anything on the fifth rank, e.g. 4..exd4 5. O-O Bc5? 6. Bxf7+ Kxf7 7. Qh5+ Ke7 8. Qxc5+ d6 9. Qxd4 nets White two pawns.

The gambit is named for Joseph Henry Blackburne (1841-1924), who apocryphally used to win shillings (about £3-4 today) from amateurs in coffee shops. It is also called the Kostić gambit after Serbian grandmaster Boris Kostić (1887-1963).

Steinitz published an analysis of the gambit in 1895, recommending 4. O-O or 4. Nxd4.

For explanation of theory tables, see theory table and for notation, see algebraic notation..

1. e4 e5 2. Nf3 Nc6 3. Bc4 Nd4

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Wikipedia has related information at Blackburne Shilling Gambit