Chess Openings Lab
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King's Pawn Game: Mengarini's Opening

Mengarini's Opening is 1.e4 e5 2.a3, a waiting move that takes b4 from Black's pieces and hints at a later b4. Black gets a free hand in the center, while White hopes to play a known structure with an extra useful pawn move on the queenside.

Moves
1.e4 e5 2.a3
ECO
C20
Engine
−0.17 · level (Stockfish 17.1, depth 20)
Played
1,232 games in our lichess sample
White scores
50.4%

Key ideas for both sides

White

  • Use the a3 move as a tempo in a reversed setup: Nc3, Nf3 and Bb5 lines resemble the Four Knights.
  • Push b4 later to gain queenside space and fianchetto with Bb2, aiming at the e5 pawn.
  • Keep a3 useful by preventing ...Bb4 pins and ...Nb4 jumps against the c2 square.
  • Do not fall behind in development; a3 is a pawn move, so follow it with knights and castling.

Black

  • Take the center with ...Nf6 and ...d5, as in the top engine line, freeing all your pieces.
  • The bishop can still go to c5, since a3 does nothing against it; ...Bc5 and ...d6 is a calm setup.
  • Develop ...Nc6 and ...Nf6 and treat it as a normal open game where White has spent a tempo.
  • After exd5 and ...Nxd5, keep an eye on Bb5 pins against the c6 knight.

Plans and pawn structure

This is an open game where Black, not White, sets the tone. With ...Nf6, ...Nc6 and ...d5, Black gets a free center and quick development. White's a3 then works like a reversed Scotch Four Knights setup, with Nc3, Nf3 and Bb5 hitting c6. If White prefers b4 and Bb2, the e5 pawn becomes the target and Black should support it with ...d6 or play ...a5 to loosen the b4 pawn.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position −0.17: level. Its three top choices for Black:

  1. −0.17 2...Nf6 3.Nc3 Nc6 4.Nf3 d5 5.exd5
  2. −0.13 2...Bc5 3.Nf3 d6 4.Bc4 Nf6 5.d3
  3. −0.04 2...Nc6 3.Nf3 Nf6 4.Nc3 d5 5.Bb5

Pawns, from White's side.

How it scores on lichess

1,232 rated lichess games reached this position; White scored 50.4%.

under 120053.3%
1200–159950.5%
1600–199945.9%

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

How to play against it

As Black, accept the invitation and play actively with ...Nf6 and ...d5 or ...Bc5. Do not copy White with a slow ...a6. You already have equality, so develop, castle and use the extra time to take the center.

Questions

What are the moves of the King's Pawn Game: Mengarini's Opening?

The King's Pawn Game: Mengarini's Opening starts 1.e4 e5 2.a3. Its ECO code is C20.

Is the King's Pawn Game: Mengarini's Opening good for White?

Stockfish 17.1 rates the position −0.17 at depth 20, which is level. In 1,232 lichess games from our sample, White scored 50.4%. A harmless offbeat choice for White players who want to avoid theory, but it hands Black easy equality.

What is the main idea of the King's Pawn Game: Mengarini's Opening?

White spends a move on a3 to keep pieces off b4 and maybe play b4 later. Black uses the time to grab the center with ...Nf6 and ...d5 or ...Bc5, reaching a comfortable open game.

What should Black play next?

The engine's first choice is Nf6, with Bc5 and Nc6 close behind. 2...Nf6 hits e4 and prepares ...d5, using White's slow move to take the center.

Updated October 2026. Sources and method.