Mengarini Variation

The Mengarini Variation answers 2...Nf6 with 3. a3, which is also known as Mengarini's Opening. It is a waiting move rather than a serious bid for an advantage. With colors reversed, the position resembles Black's after 1. e4 e5 2. Nf3 Nc6, but White has an extra move. The a-pawn rules out a Reversed Ruy Lopez with ...Bb4, although the bishop can still develop to c5. Ariel Mengarini actually preferred 2. a3 straight away, and Hugh Myers is credited with inserting 2. Nc3 Nf6 first.

The most frequent reply, 3...Bc5 4. Nf3, produces a reversed Two Knights Defense. After 4...Ng4 5. d4 exd4 6. Na4, the check on b4 that Black would use in the mirror image is not available. The quiet 4...Nc6 runs into 5. Nxe5 Nxe5 6. d4 with a small plus for White, so 4...d5 5. exd5 O-O may be Black's most reliable path. After 3...d5 4. exd5 Nxd5 5. Qh5, White has an improved Scotch Steinitz in which ...Nb4 never becomes possible. 3...Nc6 is about as popular as 3...Bc5. It allows 4. Bc4 Nxe4 with the fork trick, while 4. Nf3 leads to the Gunsberg Variation of the Scotch Four Knights. The engine rates the position as balanced, and results are close to even.