King's English Variation, Two Knights Variation, Keres Variation

The Keres Variation (ECO A23) arises when Black answers the Bremen or Carls-Bremen System, 1. c4 e5 2. Nc3 Nf6 3. g3, with 3...c6. Black does not strike at the center at once with 3...d5. The c-pawn first prepares that advance, so that if White exchanges on d5 Black can recapture with a pawn. That keeps a compact central chain which blunts the bishop on g2 and avoids the open Dragon-type structure of the Reversed Dragon. The cost is time and the d6-square, and the e5-pawn still has no defender.

White nearly always continues 4. Bg2, completing the fianchetto and waiting for ...d5 before deciding how to undermine the chain. The direct 4. d4 and 4. Nf3 both challenge e5 immediately, before Black has consolidated, and are much rarer. The engine rates the position as close to balanced with a faint preference for White, listing d4, Nf3 and Bg2 as its top choices. In practice White scores somewhat better, and decisive results far outnumber draws.