King's Pawn Game: Mengarini's Opening: what should White play?

In the position following the moves e4 e5 a3 Nf6, White most frequently continues with Nc3, which is played in 57.8% of the 713,000 recorded games. This move develops a piece while defending the e4 pawn and maintains a nearly equal engine evaluation of -0.13. By choosing Nc3, White transitions into a variation of the Mengarini Opening that often transposes into lines resembling a reversed Sicilian or a delayed Four Knights Game.

Strategic Objectives of Nc3

The move Nc3 is the primary choice for White, scoring 50.9% in practice. It reinforces the center and prepares for further development. The main line following this continuation is Nc3 Nc6 Nf3 d5 exd5 Nxd5, where the game takes on an open character. The inclusion of the pawn at a3 serves to prevent Black from utilizing the b4 square for a bishop or knight, a common theme in Mengarini's Opening.

Alternative Continuations

While Nc3 is the most popular, White has several viable alternatives. The move d3 is the second most common choice, appearing in 18.8% of games (134K recorded) with a score of 49.0%. This leads to more closed structures, typically following the line d3 d5 exd5 Nxd5 Nf3 Nc6. Other options include d4, which scores a relatively high 53.2% despite a lower engine evaluation of -0.43, and Nf3, which is seen in 3.1% of games.

Black's Defensive Setup

Black's most common response to the Mengarini setup involves challenging the center immediately or developing naturally. In the engine's top-ranked line for Nf3, Black can opt for Nf3 Nxe4 Nxe5 d5 d4 Bd6, leading to a symmetrical struggle where Black's active pieces compensate for White's slight space advantage. The move Bd3 is the least common of the major options, played in only 1.4% of games, and results in the lowest win rate for White at 45.4%.