Chessy
Petrov's Defense: Three Knights Game with Nc6 — Playing White
You've entered a quiet but sharp branch of the Petrov's Defense. After 1.e4 e5 2.Nf3 Nf6 3.Nc3 Nc6 4.Bb5, Black has several decent-looking options — and several popular traps. Statistically, this position is remarkably close: across nearly ten million games, White wins exactly 50.0%, Black wins 45.2%, and draws account for 4.7%. The engine gives +0.18, which means you have a tiny edge, but realistically this is dead level. The question is: can you steer the game toward the 50% that favours you, and dodge the move that drops to 48%? The drill below will help you practise precisely that.
Play the Petrov's Defense: Three Knights Game: Nc6 against the engine
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Try the interactive drill to practise punishing Black's inaccuracies and navigating the main line with confidence.
Create a free account →What Black Wants — And How You Counter It
Black's knight on f6 already pressures your e4-pawn, and the knight on c6 eyes the centre. After 4.Bb5 you are pinning the knight on c6, which interferes with Black's plan to …d5 (the classic Petrov break). If Black plays …d6, they consolidate but lose time; if they lash out with …Nd4 or …Bc5, the position sharpens. Your job is simple: complete development, castle quickly, and keep the pin on the c6-knight as long as it is useful. The engine's top recommendation, Bd6, shows that Black should unpin and prepare to castle — a modest, healthy plan. Against almost everything else you can claim a small practical edge simply by developing naturally.
The One Reply You Should Welcome: …a6
Statistics show that 1,927,324 games have seen Black play 4…a6 — the third-most-popular move. Strikingly, White scores 53.3% here, your best winning percentage against any major reply. Black's idea is to force the bishop to decide its fate: if you retreat to a4, the pin is gone; if you exchange on c6, Black opens the b-file. Still, the numbers don't lie — most White players come out ahead. The engine classifies …a6 as an inaccuracy, costing Black about 0.5 pawns compared to the best move. Trust the statistics: when Black kicks your bishop, you are the one with the better chances.
Avoid the Popular Traps: …d6 and …Nd4
The single most-played move in this position is 4…d6 (2,472,679 games), but it is also a clear mistake. The engine says it loses roughly 0.8 pawns compared to 4…Bd6, and White scores a slightly below-average 48.5% — mostly because players don't know how to punish it. After 4…d6, Black's pawn chain is passive and the bishop on c8 is blocked. Develop with O-O, d3, and prepare to strike in the centre. Similarly, 4…Nd4 (654,033 games) is an inaccuracy costing about 0.7 pawns. The knight looks aggressive, but after 5.Nxd4 exd4 you recapture with the knight and Black's d4-pawn becomes a target. In both cases, patience and simple development yield a tiny but stable edge.
The Critical Continuation: When Black Plays …Bd6
Black's best move is 4…Bd6, the engine's top choice, and it leads to a solid if unambitious setup: 4…Bd6 5.O-O O-O 6.d3. From here the game is balanced — White scores 49.4% across 318,465 games, basically a toss-up. The bishop on d6 is slightly passive but keeps the position solid. Your plan as White: complete development with Re1, Bg5 or Bxc6, and look for a favourable moment to play d4. The position resembles a quiet Italian or Spanish but with the knights already tangled. Do not overreach — the engine calls this dead level for a reason, and pressing too hard will hand Black counterplay.
Results across 9,813,834 Lichess games
| Most-played continuation | Games | White wins |
|---|---|---|
| d6 | 2,472,679 | 48.5% |
| Bc5 | 2,286,750 | 48.3% |
| a6 | 1,927,324 | 53.3% |
| Bb4 | 1,423,197 | 50.0% |
| Nd4 | 654,033 | 48.1% |
| Bd6 | 318,465 | 49.4% |
Frequently asked questions
Is the Petrov's Defense: Three Knights Game good for White?
Statistically it is virtually even. White wins 50.0% of games, Black wins 45.2%, and draws are rare at only 4.7%. The engine gives +0.18, a tiny edge that is not enough to claim advantage. You are not worse, but you should not expect to crush a well-prepared opponent.
What is the best move for Black against 4.Bb5?
The engine's top choice is 4…Bd6, unpinning the knight and preparing to castle. It scores 49.4% for White across 318,465 games — essentially balanced. The three most common mistakes are 4…d6, 4…a6, and 4…Nd4, each giving White a measurable advantage.
How should White respond to 4…a6?
White scores an excellent 53.3% against 4…a6, which is classified as an inaccuracy. You can retreat the bishop to a4, keeping the pin, or exchange on c6 — both are playable. The key is to develop quickly and use Black's slightly wasted tempo.
Why is 4…d6 considered a mistake?
The engine says 4…d6 loses about 0.8 pawns compared to 4…Bd6. It is the most popular move (over 2.4 million games) but White's winning chances are below 50% only because many White players do not exploit the error. Simple development and a timely d4-push give you a stable plus.