|Petrovīs Defence (sometimes spelled Petrof or Petroff) is the chess opening|
1.e4 e5 2.Nf3 Nf6
Though this symmetrical response has a long history, it was first popularized by Alexander Petrov — a Russian chess player of the mid-19th century. In recognition of the early investigations by the Russian masters Petrov and Carl Jaenisch, this opening is called the Russian Game in some countries. The Petrov has a reputation of being solid. The Black counterattack in the center avoids the Ruy Lopez and Giuoco Piano and is often played by Black with the aim to draw.
If White defends his attacked king pawn with 3. Nc3, Black can obtain equal chances by transposing into the Four Knights Game with 3...Nc6 or by entering the Three Knights Game with 3...Bb4.
White usually replies more aggressively with 3.Nxe5 or 3.d4.
After 3. Nxe5, Black should not continue to copy Whiteīs moves and try to restore the material balance immediately with 3...Nxe4? because after 4. Qe2 White will either win material (4...Nf6?? 5.Nc6+ wins Blackīs queen, and after 4...d5 5.d3 Qe7 6.dxe4 Qxe5 7.exd5 Black loses a pawn), or obtain a superior position (4...Qe7 5.Qxe4 d6 6.d4 f6 7.Nc3 dxe5 8.Nd5 Qd6 9.Bf4 Nd7 10.0-0-0 and White has a big advantage). Black usually plays 3...d6. White can make a speculative sacrifice by trying the Cochrane Gambit with 4.Nxf7?!, but more often the game follows the main line 4.Nf3 Nxe4 5.d4 d5 6.Bd3 where White will try to drive Blackīs advanced knight from e4 with moves like c2-c4 and Re1. White can instead force simplification with Laskerīs 5.Qe2. This is generally only good enough for a draw, but Black must avoid this line if he is playing for a win. A third possibility explored by Keres is 5.c4.
Steinitz favored 3.d4. Black can capture either white pawn. After 3...exd4 4.e5 (4.Bc4 transposes into the Bishopīs Opening) Ne4 5.Qxd4 d5 6.exd6 Nxd6 White has some advantage. Blackīs other capture is probably better, since 3...Nxe4 4.Bd3 d5 5.Nxe5 followed by 5...Nd7 or 5...Bd6 gives Black good chances.
Karpov, Yusupov, and Marshall have frequently played the Petrov as Black.
The ECO codes for Petrovīs Defence are C42 (for White moves other than 3.d4) and C43 (for 3.d4).