Petrov's Defence

Rather than defend e5, Black counterattacks e4. This is the Russian game, aka Petrov's or Petroff's defence, a solid if drawish opening.^[1]

White's typical plan is to attack the centre, usually leading to a trade of pawns. Alternatively they may gambit their e4 pawn, or defend it and perhaps hope for a transposition.

3. Nxe5 is the main line, the Classical variation. As Black didn't defend their pawn, White takes it. Black can recover it, but not immediately on account of dangerous tactics resulting from 3...Nxe4!? 4. Qe2!, exploiting the open e-file (including the famous trap, 4...Nf6?? 5. Nc6+ winning the queen). The best line is 3...d6, chasing White's knight away, after which 4...Nxe4 is safe because if 5. Qe2 Qe7 defends the knight. 3...Nc6?!, the aggressive Stafford gambit, is the most common reply in amateur games. Black gives up a pawn for open lines and a sharp attack.

3. d4, the Modern attack, was advocated by Steinitz.^[2] Of the two captures, 3...Nxe4 is most common. 3...exd4 is playable but after 4. e5 Black falls behind while their knight gets kicked about (4...Ne4 5. Qxd4 d5 6. exd6 Nxd6⩲).

3. Bc4?!, the Italian variation, leaves White's e4 pawn undefended. It's usually played with the idea of sacrificing it for development: 3...Nxe4 4. Nc3?!, the Boden-Kieseritzky gambit. Instead, 3...Nc6 transposes into a Two knights defence of the Italian game.

White may wish to prevent ...Nxe4, though taking the time to defend their pawn gives Black the chance to defend theirs too.

3. Nc3 is the Three knights variation. White develops a piece and invites Black to transpose to a Four knights with 3...Nc6. This option is sound when White wants to avoid the sharp lines of Petrov's Defence. 3...Bb4 avoid transposing, pressures the knight on c3 and makes the game a little more active.

3. d3 is, according to statistics, much more effective than it looks. White builds a strong fortress and Black must now defend his pawn. The game usually ends up looking like a Hanham variation of the Philidor with colours reversed (3...Nc6 4. Be2 d5 5. Nbd2 Bc5⩱) or White adopts a King's Indian attack-style setup with g3 and Bg2.

2...Nf6 is a very old opening, appearing in the 15th/16th century Göttingen manuscript, the earliest manuscript dedicated to modern chess.

However, it was largely overlooked until the 19th century. Jaenisch (1813―1872) levels (his typical, bombastic) criticism at previous attempts to characterise the opening in his 1842 book^[3]:126-147:

The fate of this opening has been somewhat "bizarre." Proclaimed faulty from the 16th century (compare Damiano, Lopez, and Gianutio), it has been entirely thrown on one side, and has only since appeared in the books; which content themselves with reproducing, without change, the ancient analysis of the classics. Cozio, in truth, that frivolous genius, who saw everything superficially, without diving into it, at last briefly corrected the fallacies of the original analysis in question; but, curious enough, was not himself aware of the importance of his observation, which passed altogether unnoticed by later writers.

—Carl Jaenisch (translation: Walker)^[3]

It was Alexander Petrov (1794―1867) and Jaenisch's analyses that led to the rejuvenation of opening in the 19th century (and it's after these two Russians the opening gets its appellation). Jaenisch highlights Petrov's independent (re-)discovery of Cozio's 3. Nxe5 d6! (over 3...Qd7).^[3]

Jaenisch also credits Petrov with 3. d4 as White,^[3] the line later advocated by Steinitz in his 1889 book.^[2]

For explanation of theory tables, see theory table and for notation, see algebraic notation.

1. e4 e5 2. Nf3 Nf6

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Wikipedia has related information at Petrov's Defence

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.