Master the Petrov Defense: d4 as Black

By playing 3...Nxe4 instead of 3...exd4, you've kept the tension. You have a knight on e4 that White must deal with, and your dark-squared bishop hasn't committed yet. The central pawn on e5 is still undefended — that's the first thing White will look at. Your job is to consolidate the knight on e4, get your pieces out, and not let White's space advantage in the centre grow too large. The engine's favourite response is the recapture 4.Nxe5, because it attacks your knight immediately and opens lines. The statistics show that White scores about 50.4% after this move — a balanced fight. The real scoring differences appear in White's weaker choices, which we'll cover below.

If White plays the engine's first choice 4.Nxe5, the game continues 4...d5 5.Nd2 Bd6. Notice the ideas behind each move: you advance 4...d5 to kick the knight on e4 and take control of the centre, and then 5...Bd6 develops with a threat against the knight on e5. White's knight on d2 blocks their light-squared bishop, but it also supports your own e4-knight — White will likely capture it next move. This is a perfectly playable position: the engine says +0.41, a tiny edge for White, but the statistics from over 210,000 games show White scores only 50.4%, so the practical winning chances are nearly equal. Focus on completing development and castling quickly.

More than 311,000 games have seen 4.dxe5 — it's White's single most popular choice, even though it isn't the engine's top recommendation. White takes the pawn and asks what you'll do about the knight on e4. The answer is straightforward: retreat the knight or trade it. A common continuation is 4...Nc5, heading for the outpost on e6 or supporting a quick ...d7-d6. From this position White scores 50.5%, almost identical to the engine line. The takeaway: 4.dxe5 is nothing to fear. You get a solid game with easy development, and the engine still assesses White's advantage at the same +0.41. Just don't try to hold the knight on e4 with ...d5 too early — White can trade and leave you with a weak pawn.

Two moves stand out as genuine errors you can exploit. The most-played of these is 4.Bc4 (79,834 games, White scores 57.1%), but the engine calls it a mistake — White loses about 1.7 pawns of advantage by playing it, and the better move was 4.Bd3. After 4.Bc4, you can counter by attacking the bishop with ...d5, gaining time, or by playing ...Nc5 to hit it again. Even though White scores well in practice, the objective assessment says you should have better chances if you know the right response. The other error is 4.Nc3 (just 5,082 games, White scores 45.1%). This loses about 1.8 pawns — White lets you trade knights or simply retreat to f6, and your central presence remains strong. Look for these moves from your opponent and punish them confidently.