Grünfeld Defense: Three Knights Variation, Petrosian System
The Petrosian System is 4...Bg7 5.Bg5 in the Three Knights Grünfeld, pressuring the f6 knight with the king knight already on f3. Black often kicks the bishop with ...Ne4 or hits d4 with ...c5, while White seeks a solid center and play against d5.
- Moves
- 1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3 Bg7 5.Bg5
- ECO
- D91
- Engine
- +0.07 · level (Stockfish 17.1, depth 20)
- Played
- 625 games in our lichess sample
- White scores
- 52.0%
Key ideas for both sides
White
- Answer 5...Ne4 with 6.Bf4 and recapture on c3 with the pawn.
- After 5...c5, dxc5 and Bxf6 can win a pawn if Black is careless.
- e3 and cxd4 support the center after trades.
- Keep the bishop active outside the pawn chain.
Black
- 5...Ne4 hits the bishop and trades knights, as the top engine line shows.
- 5...c5 counters at once; ...Qa5 pins and regains the pawn.
- ...Na6 develops after the trades and heads for c5.
- Castle and keep the long diagonal open for the g7 bishop.
Plans and pawn structure
White's Bg5 hits f6, but Black can kick it with ...Ne4. After ...Nxc3 bxc3, White has a center with c3, d4 and e3, and Black plays ...c5 to break it. In the ...c5 line, Black gives a pawn for activity with ...Qa5 and ...Na6. The game is balanced and flexible.
What the engine plays from here
Stockfish 17.1 at depth 20 rates the position +0.07: level. Its three top choices for Black:
- +0.07 5...Ne4 6.Bf4 Nxc3 7.bxc3 c5 8.e3
- +0.21 5...c5 6.dxc5 Qa5 7.Bxf6 Bxf6 8.cxd5
- +0.47 5...c6 6.cxd5 Nxd5 7.e4 h6 8.Bd2
Pawns, from White's side.
How it scores on lichess
625 rated lichess games reached this position; White scored 52.0%.
Light: White wins. Grey: draws. Dark: Black wins. About the sample.
How to play against it
As Black, play 5...Ne4 or 5...c5 and keep pressure on d4. Avoid 5...c6, which is more passive. As White, keep d4 solid and develop calmly.
Questions
What are the moves of the Grünfeld Defense: Three Knights Variation, Petrosian System?
The Grünfeld Defense: Three Knights Variation, Petrosian System starts 1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3 Bg7 5.Bg5. Its ECO code is D91.
Is the Grünfeld Defense: Three Knights Variation, Petrosian System good for White?
Stockfish 17.1 rates the position +0.07 at depth 20, which is level. In 625 lichess games from our sample, White scored 52.0%. A flexible line for White players who like slow positional play, while Black needs to know the ...Ne4 and ...c5 ideas.
What is the main idea of the Grünfeld Defense: Three Knights Variation, Petrosian System?
White targets the f6 knight with the bishop. Black answers with ...Ne4 to trade or ...c5 to counterattack d4.
What should Black play next?
The engine's first choice is Ne4, with c5 and c6 close behind. 5...Ne4 kicks the bishop and trades knights, easing Black's game.
Related lines
Updated October 2026. Sources and method.