Three Knights Opening

The Three Knights Opening, also called the Three Knights Game, arises when White answers 2...Nc6 with 3. Nc3 instead of committing the king's bishop. The move follows the knights-before-bishops principle formulated by Emanuel Lasker: both white knights normally belong on c3 and f3 anyway, so White develops them first and keeps the choice of Bb5 or Bc4 and the timing of d2-d4 in reserve. Although 3. Nc3 threatens nothing, it leaves Black few attractive ways to avoid symmetry. About half of all games continue 3...Nf6, transposing to the Four Knights Game, so the Three Knights name chiefly covers Black's alternatives.

The bishop moves are the most direct of these, and each has a drawback. The second most frequent reply, 3...Bc5, allows the center fork trick 4. Nxe5 Nxe5 5. d4, and after 5...Bd6 6. dxe5 Bxe5 material is level but Black's e5 outpost has disappeared; tournament practice has favored White, though online results with 3...Bc5 are close to even. The pin 3...Bb4 is premature while White's d-pawn is unmoved, because 4. Nd5 gains time against the bishop; 4...Nf6 is the Schlechter Variation.

Quieter tries carry their own costs. After 3...d6, White can play 4. d4, giving Black a cramped game of the Philidor's Defense type. The Steinitz Defense, 3...g6, prepares ...Bg7 but spends an extra tempo compared with ...Nf6 followed by a one-move bishop development; the principal line is 4. d4 exd4 5. Nd5, the Steinitz-Rosenthal Variation. Steinitz won with the fianchetto against Rosenthal in 1873 in a game that reached the same setup through 2. Nc3 and saw 5. Nxd4.

The most combative choice is 3...f5, the Winawer Defense, sometimes called the Gothic Defense, in which Black offers the f-pawn. The main reply is 4. d4, while 4. Bb5 transposes to the Schliemann Defense of the Ruy Lopez. Taking with 4. exf5 is regarded as clearly good for White, although Black can generate practical chances at amateur level.

At master level the Three Knights is now almost never seen as a distinct opening, since Black players looking for activity prefer other options, including sharper lines within the Four Knights. It remains very common online, and its results there are close to even, matching an engine assessment of a roughly balanced position.