Chess Openings Lab
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Sicilian Defense: Mengarini Variation

The Mengarini Variation is 2.a3, a quiet pawn move that prepares b4 against the Sicilian. White keeps options open, while Black can develop freely with ...g6 and ...Bg7 or ...Nc6 and aim for easy central play.

Moves
1.e4 c5 2.a3
ECO
B20
Engine
−0.30 · a slight edge for Black (Stockfish 17.1, depth 20)
Played
3,062 games in our lichess sample
White scores
51.9%

Key ideas for both sides

White

  • Use b4 to undermine Black's c5 pawn once Black's pieces are committed.
  • Transpose to an Open Sicilian with Nf3 and d4, where a3 may be a useful waiting move.
  • Against ...Nc6 and ...g6, Bb5 and e5 make White's play more active.
  • Keep the center flexible and develop quickly; a3 is slow, so tempo matters.

Black

  • 2...g6 with ...Bg7 builds a strong kingside and watches b2 along the long diagonal.
  • ...Nc6 develops and keeps a grip on d4 and e5.
  • If White opens with d4, recapture on d4 and develop as in a normal Open Sicilian.
  • Watch for b4 ideas; keep c5 supported or exchange it before White can undermine it.

Plans and pawn structure

White's a3 gives the game an unusual flavor. If White plays b4, Black must decide whether to take or defend c5. If White transposes with Nf3 and d4, the extra a3 move takes the b4 square away from Black's bishop and knights. Black can play a fianchetto with ...g6 and ...Bg7 or ...Nc6 and ...d6, then fight for d4. The game often settles into Open Sicilian structures with a small difference on the queenside.

Where the engine's main line heads: Open Sicilian: White traded the d-pawn for Black's c-pawn. An Open Sicilian: White traded the d-pawn for Black's c-pawn. White has a lead in development and the d-file, Black has the half-open c-file and two central pawns.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position −0.30: a slight edge for Black. Its three top choices for Black:

  1. −0.30 2...g6 3.Nf3 Bg7 4.d4 cxd4 5.Nxd4
  2. −0.15 2...Nc6 3.Nf3 g6 4.Bb5 Bg7 5.O-O
  3. −0.11 2...d6 3.Nc3 Nc6 4.Nf3 g6 5.d4

Pawns, from White's side.

How it scores on lichess

3,062 rated lichess games reached this position; White scored 51.9%.

under 120055.3%
1200–159949.5%
1600–199951.7%
2000 and up53.4%

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

How to play against it

As Black, develop with ...g6 and ...Bg7 or ...Nc6 and ...d6. Do not overreact to a3; just make sure c5 is not a target. If White plays d4, take and develop normally.

Questions

What are the moves of the Sicilian Defense: Mengarini Variation?

The Sicilian Defense: Mengarini Variation starts 1.e4 c5 2.a3. Its ECO code is B20.

Is the Sicilian Defense: Mengarini Variation good for White?

Stockfish 17.1 rates the position −0.30 at depth 20, which is a slight edge for Black. In 3,062 lichess games from our sample, White scored 51.9%. A low-theory option for White, but Black gets comfortable equality by developing pieces and fighting for d4.

What is the main idea of the Sicilian Defense: Mengarini Variation?

White plays a3 to prepare b4 and keep options open. Black develops normally, usually with ...g6 and ...Bg7 or ...Nc6, and has an easy game.

What should Black play next?

The engine's first choice is g6, with Nc6 and d6 close behind. 2...g6 prepares ...Bg7, aiming at b2 and the center and making b4 less attractive.

Updated October 2026. Sources and method.