The Four Knights Game is a chess opening that begins with the moves:
- 1. e4 e5
- 2. Nf3 Nc6
- 3. Nc3 Nf6
This is the most common sequence, but the knights may develop in any order to reach the same position.
The opening is fairly popular with beginners who strictly adhere to the opening principle: "Develop knights before bishops." It was one of the workhorses in the family of the Open Game, at even the highest levels, until World War I. Thereafter it fell by the wayside, along with a number of open games. In this period ambitious players explored the Ruy Lopez, believing it a better attempt for White to exploit the advantage of the first move. In the 1990s, this opening saw a renaissance, and is now seen in the praxis of players from beginner to grandmaster.
The Four Knights usually leads to quiet positional play, though there are some sharp variations. The ECO codes for the Four Knights Game are C49 (the Symmetrical Variation, 4.Bb5 Bb4), C48 (4.Bb5 without 4...Bb4), and C47 (alternatives to 4.Bb5).
White's most common move is 4.Bb5, the Spanish Variation, after which Black has three major alternatives.
The first of these is 4... Bb4, the Symmetrical Variation. It often results in a quick draw, but it is possible for either side to play for a win.
Black can play more aggressively by 4... Nd4, the Rubinstein Variation. White cannot win a pawn with 5.Nxe5, since Black regains the pawn with the advantage of the bishop pair after 5...Qe7 6.Nf3 (6.f4 Nxb5 7.Nxb5 d6) Nxb5 7.Nxb5 Qxe4+ 8.Qe2 Qxe2+ 9.Kxe2 Nd5! 10.c4 a6! White most often plays 5.Ba4, when Black usually continues in gambit fashion with 5...Bc5!? 6.Nxe5 0-0 7.Nd3 Bb6 8.e5 Ne8 followed by ...d6. Another line, which discourages many ambitious Black players from playing the Rubinstein, is 5.Nxd4 exd4 6.e5 dxc3 7.exf6 Qxf6 (7...cxd2+?! 8.Bxd2 Qxf6 9.0-0 is dangerous for Black) 8.dxc3 Qe5+. This often leads to a quick draw after 9.Qe2 Qxe2+.
In recent years, Black has tried 4... Bd6!? with success. That move takes the sting out of 5.Bxc6, which is met with 5...dxc6 with a good game. If White plays quietly, Black will regroup with ...0-0, ...Re8, ...Bf8, and ...d6.
The move 4.d4
If White plays 4.d4, the Scotch Four Knights Game arises. This leads to a more open position, which can also be reached from the Scotch Game, e.g. 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Nf6 5.Nc3. This variation was played in the fifth game of the 1996 Deep Blue vs. Garry Kasparov match.
One reason White may choose the Four Knights (3.Nc3) move order over the Scotch (3.d4), besides fearing that after 3.d4 exd4 4. Nxd4 Black may choose 4...Bc5 or 4...Qh4, is that White may want to play the Belgrade Gambit (1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.d4 exd4 5.Nd5!?). It is not possible to reach the Belgrade from the Scotch. However, the Belgrade is a distant second in popularity to 5.Nxd4.
The move 4.Bc4?!
A further possibility is 4.Bc4?!, the Italian Four Knights Game, though this line is regarded as inferior according to Pinski, and an outright mistake by IM Larry D. Evans. Black can preserve the symmetry by 4...Bc5, leading to the quiet Giuoco Pianissimo. That position can also be reached via the Giuoco Piano by 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Nc3 Nc6. The line is a favorite among younger players due to its simple and easy development, but has also been used successfully by Nigel Short against Antoaneta Stefanova.
After 4.Bc4?!, the pseudo-sacrifice of a knight with 4...Nxe4!, the fork trick, is a serious try for an advantage. Then 5.Bxf7+?, though superficially attractive, relinquishes the bishop pair and central control to Black. Better is 5.Nxe4, when 5...d5 regains the piece with an excellent game, e.g., 6.Bd3 dxe4 7.Bxe4 Bd6 8.d4 Nxd4 9.Nxd4 exd4 10.Qxd4 O-O 11.Be3 (11.0-0?? Bxh2+ wins) Qe7 (Tartakower–Atkins, London 1922) and now the natural 12.O-O Be5 would be awkward for White. In the above line, more ambitious is 8...exd4 9.Nxd4 0-0!?, as in a match game between Siegbert Tarrasch and Emanuel Lasker in 1916, which led to a Black win in 23 moves.
The move 4.a3
The quiet waiting move 4.a3 (called the Gunsberg Variation) is a specialty of Polish Grandmaster Paweł Blehm. White gets no advantage after 4...d5 (a Scotch Four Knights Game Reversed).
The move 4.Nxe5?
A dubious gambit is 4.Nxe5?!, the so-called Halloween Gambit. After 4...Nxe5 5.d4, White tries to seize the center with his pawns and drive the Black knights back to their home squares. Grandmaster Larry Kaufman says that this line is refuted by 5...Nc6 6.d5 Bb4! 7.dxc6 Nxe4 8.Qd4 Qe7, which he attributes to Jan Pinski. According to Max Euwe's opening series volume 11, Black has a decisive advantage after 4...Nxe5 5.d4 Ng6 6.e5 Ng8 7.Bc4 d5 8.Bxd5 c6.
The move 4.g3
Igor Glek has favored 4.g3, preparing development of the bishop to g2. According to Pinski, Black's main responses are 4...Bc5 and 4...d5, both of which are reckoned to equalize for Black. A Halloween Gambit style 4...Nxe4 has also been tried at the grandmaster level as in two games between Ilya Smirin and Bartłomiej Macieja.