Petrov's Defense: Three Knights Game

About this variation

White plays 3. Nc3, defending e4 and inviting Black into a Four Knights Game or independent lines.

The Three Knights Game in the Petrov is 1. e4 e5 2. Nf3 Nf6 3. Nc3. White defends the e4 pawn with a knight instead of taking on e5 or opening the center, and invites Black to play 3...Nc6, which transposes to the Four Knights Game. Black can also play 3...Bb4, keeping the game in independent territory.

After 3...Nc6, the game reaches the Four Knights, where White's main lines include 4. Bb5, the Spanish Four Knights, and 4. d4, the Scotch Four Knights. After 3...Bb4, Black pins the knight and puts pressure on e4, and White often replies 4. Nxe5 or 4. Bc4 for active play.

White's plans include quick development with Bb5 or Bc4, O-O and d3 or d4, and play in the center. White usually aims for a small but lasting edge without much risk, using the extra tempo in a symmetrical position.

Black's ideas include ...Bb4 to pin the knight, ...O-O and ...d6 for solid development, and ...Nd4 in some lines to challenge White's pieces. Black aims for a balanced position with no weaknesses.

The Three Knights Game is a calm way for White to avoid the main Petrov theory. It often leads to positions where both sides have played natural moves and the game is decided in the middlegame.

This line suits White players who like simple development and are happy in Four Knights positions. Black players should know whether they want to transpose with 3...Nc6 or play 3...Bb4, since each leads to a different type of game.

After 3...Bb4 4. Nxe5 O-O 5. Be2 Re8, Black regains the e4 pawn or gets strong pressure for it, so the line rarely gives White much. Many players with White therefore use 3. Nc3 mainly as a way to reach the Four Knights, where they already know the plans.

It is one of the main lines of the Petrov's Defense.