The Four Knights Game is a double King Pawn opening (1. e4 e5) where both sides develop their Knights first, following the classic principle Knights Before Bishops. This means Knights typically do best on f3/f6 and c3/c6, while Bishops have several good squares available to develop. The usual move order is 1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6, although this may be reached by transposition from the Vienna Game (1. e4 e5 2. Nc3). The Four Knights (4N) is a safe and solid choice for beginners and juniors, aiming for straightforward development, yet it is not common at the GM level since the quiet center and symmetrical piece play give White less of a potential opening advantage compared to more dynamic lines.
The chessgames.com database has 3,764 Four Knights games, with these statistics for White's fourth move: 4. Bb5 56%, 4. d4 27%, 4. Bc4 13%, and 4. g3 10%. Don't try to memorize these percentages, but it's helpful to consider how often the different main lines are played when studying openings.
A. 4. Bb5
This is the Spanish Four Knights, taken from the Ruy Lopez (1. e4 e5 2. Nf3 Nc6 3. Bb5) which is also called the Spanish Game. White often chooses this move order so that Black can't defend the Pe5 with … f6 once the King Knight is on that square. After 4. Bb5 Black can play the symmetrical 4 … Bb4 (often leading to 5. 0-0 0-0 6. d3 d6), or the Rubinstein Variation 4 … Nd4 unbalancing the game. The play is very different from the Ruy Lopez since White cannot create a classic Pawn center with c2-c3 and d2-d4, plus the center remains quiet after d2-d3 instead.
B. 4. d4
The Scotch Four Knights is similar to the Scotch Game (1. e4 e5 2. Nf3 Nc6 3. d4) with the extra Knight moves before White advances d2-d4. Here White wants Black to give up the center by trading the Pd4 for the Pe5, leaving White with the only center Pawn at e4. Black often trades … exd4 and later advances … d7-d6; the White Pe4 against the Black Pd6 is called a Scotch Center and assures White an advantage in space. One typical Main Line is 4. d4 exd4 5. Nxd4 Bb4 6. Nxc6 bxc6 7. Bd3 (defending the Pe4) d5 8. exd5 cxd5 with chances for both sides.
C. 4. g3
White will fianchetto the King Bishop on g2, leading to the Glek Line named after GM Igor Glek from Germany. This variation is very similar to a King's Indian Attack (Nf3, g3, Bg2 & 0-0) except White has already established a center Pawn with 1. e4. A primary drawback of 4. g3 is that Black can reply 4 … d5 opening lines for development while making White give up the center with exd5. Play usually continues 5. exd5 Nxd5 6. Bg2, and now Black gets a good game with 6 … Nxc3 or 6 … Nde7 (followed by 7 … g6 & 8 … Bg7), while 6 … Be6 (intending 7 … f6) scores worse as White can pressure Black's center with Re1 and d2-d4.
D. 4. Bc4
White's King Bishop usually does very well on c4, aiming at Black's weak point on f7, like the Giuoco Piano (1. e4 e5 2. Nf3 Nc6 3. Bc4) and Bishop's Opening (1. e4 e5 2. Bc4). In the Four Knights, 4. Bc4?! is a mistake allowing Black to play 4 … Nxe4! which is a sham sacrifice as 5. Nxe4 d5 (Fork Trick) regains the piece and Black is better. Here 6. Bxd5 Qxd5 7. d3 Bg4 is common, or 6. Bb5 dxe4 7. Nxe5 Qd5/Qg5 and Black has more space. All 1. e4 e5 players should know this stock tactic, which also shows up in the Two Knights Defense (1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6) after 4. Nc3?! Nxe4! with the same Fork Trick idea by transposition.
E. 4. Nxe5
The Halloween Gambit is a risky, uncommon line where White sacrifices a piece for an advantage in space and development, leading to an immediate attack against Black's King. After 4. Nxe5!? Nxe5 5. d4 Black retreats 5 … Ng6 6. e5 Ng8 and hopes to reach an endgame where the extra piece will prevail. Another plan is 5 … Nc6 6. d5 Nb8 7. e5 Ng8 hanging on, although here Black could play it safe and return the piece with 6 … Qe7 or 6 … Bb4 for an even game.
F. Other Fourth Moves
Passive moves like 4. d3, 4. Be2 and 4. a3 are met by 4 … d5 and Black has already equalized, thus they are rarely played. One move to avoid is 4. Bd3?! blocking the d Pawn and causing bad congestion in White's center.
The Four Knights is a great opening for all players starting out at chess, as it is easy to learn and gives both sides a very solid game. Good luck!