Chess Openings Lab
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Petrov's Defense: Cozio Attack

The Cozio Attack is 3.Nxe5 d6 4.Nf3 Nxe4 5.Qe2, putting White's queen on the e-file against the knight on e4 and the king behind it. White hopes for a small endgame edge after queens come off, while Black must answer the pin at once with 5...Qe7.

Moves
1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.Qe2
ECO
C42
Engine
+0.17 · level (Stockfish 17.1, depth 20)
Played
1,182 games in our lichess sample
White scores
50.6%

Key ideas for both sides

White

  • Hit the pinned knight with d3. If Black has not covered the e-file, the knight cannot move without exposing the king.
  • After 5...Qe7 6.d3 Nf6, develop with Nc3 and recapture on e2 with the bishop to reach a queenless middlegame.
  • Use the extra tempo in the endgame: d4, then Bf4 or Bg5, with a small lead in space.
  • Watch for Nc3 and Nd5 jumps against the queen on e7 if Black delays the trade.

Black

  • Play 5...Qe7 to break the pin. Moves like ...f5 or ...d5 leave the knight pinned and d3 wins it.
  • Retreat with ...Nf6 after d3, then trade queens with ...Qxe2+ to remove White's only active idea.
  • Develop with ...Bd7, ...Nc6 and ...Be7, then castle; the endgame is level and simple.
  • Keep pawns on f7 and d6 for now; loosening the kingside gives White's knights targets.

Plans and pawn structure

This line usually turns into an early queenless middlegame. White plays d3, Nc3 and Bxe2 after the trade, then d4 for space and quick development with a small initiative. Black aims for quiet equality: ...Nf6, ...Bd7, ...Nc6 and ...Be7, with the king staying near the center once the queens are gone. Neither side has pawn weaknesses, so the side that activates rooks first on the e-file or d-file gets the easier game.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position +0.17: level. Its three top choices for Black:

  1. +0.17 5...Qe7 6.d3 Nf6 7.Nc3 Qxe2+ 8.Bxe2
  2. +2.77 5...f5 6.d3 d5 7.dxe4 fxe4 8.Nc3
  3. +2.86 5...d5 6.d3 f5 7.Bg5 Be7 8.Bxe7

Pawns, from White's side.

How it scores on lichess

1,182 rated lichess games reached this position; White scored 50.6%.

under 120053.8%
1200–159950.8%
1600–199949.4%
2000 and up50.0%

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

How to play against it

As Black, answer 5.Qe2 with 5...Qe7 and nothing else. Do not defend the knight with ...f5 or ...d5: after d3 it is pinned and lost. After 6.d3 retreat ...Nf6, trade queens on e2, and develop. The ending is fully playable and easy to handle.

Questions

What are the moves of the Petrov's Defense: Cozio Attack?

The Petrov's Defense: Cozio Attack starts 1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.Qe2. Its ECO code is C42.

Is the Petrov's Defense: Cozio Attack good for White?

Stockfish 17.1 rates the position +0.17 at depth 20, which is level. In 1,182 lichess games from our sample, White scored 50.6%. A low-risk drawing weapon for White and a trap for careless Black players, so Black only needs to remember ...Qe7.

What is the main idea of the Petrov's Defense: Cozio Attack?

White pins the e4 knight to the king with Qe2 and threatens d3 to win it. Black must break the pin with ...Qe7, and after ...Nf6 and a queen trade on e2 the game becomes a level, quiet endgame.

What should Black play next?

The engine's first choice is Qe7, with f5 and d5 close behind. 5...Qe7 neutralizes the pin on the e-file, so the knight can retreat when d3 comes.

Updated October 2026. Sources and method.