Anderssen's Opening: what should Black play?

In Anderssen's Opening (ECO A00), Black faces the modest flank push 1. a3 and holds comfortable equality with several standard setups. The engine prioritizes natural development with Nf6, which yields a slight -0.16 evaluation across 481K recorded games (10.3% of the database). By developing the kingside knight immediately, Black remains completely flexible regarding central pawn placement while neutralizing any modest tempo advantage White sought to gain.

Engine Evaluation and Central Alternatives

While Nf6 carries the lowest evaluation at -0.16, human play leans heavily toward immediate central occupation. The classical strike e5 is the most frequent choice, appearing in 40.7% of games (1.89M recorded) with White scoring 50.0% points and an evaluation of -0.11. Similarly, d5 accounts for 32.7% of games (1.53M recorded) with an evaluation of +0.01, allowing White to score 50.2%. Both moves claim the center directly, though Nf6 avoids committing central pawns before White reveals a definitive setup.

Illustrative Continuations

Following the top-rated Nf6, the engine illustrates a flexible Queenside approach via the continuation Nf6 Nf3 c5 e3 d5 b4, where White uses the initial flank thrust to contest the c5 square. For players who prefer immediate flank pressure against White's center, c5 scores well for Black, holding White to 49.4% points across 395K recorded games (8.5%) and leading into c5 e3 d5 d4 cxd4 exd4 with a -0.15 evaluation.

Hypermodern Setups

Black can also opt for a fianchetto structure using g6, which scores effectively by holding White to 47.3% points across 363K games (7.8% of recorded play). Rated at -0.15, this approach can develop along the line g6 d4 Nf6 c4 Bg7 e3. Because 1. a3 does not influence the center, Black retains the freedom to choose classical or hypermodern responses without tactical hindrance.