O'Kelly Variation, Maróczy Bind

Against the O'Kelly, 3. c4 puts the c- and e-pawns in place before d4 is played. This builds the Maróczy structure, named after Géza Maróczy, at once. The pawns on c4 and e4 control d5 and make the freeing ...d5 hard to achieve. The early c4 also takes some of the point out of 2...a6, which was meant to deny b5 to White's pieces in an open position. Wikibooks calls it White's most aggressive answer to the O'Kelly. The engine gives White a slight edge, and White outscores Black in online games.

Black has three main replies. On Lichess the most frequent is 3...Nc6, which can continue 4. d4 cxd4 5. Nxd4 e5. That reaches the position of the Geller Line, which also arises from 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 a6 5. c4 e5. The Paulsen Line, 3...e6, is the choice most common at master level. White usually meets it with 4. Nc3, and the game can transpose to a Kan with c4 already played. The Robatsch Line, 3...d6, keeps the pawns flexible. Against the bind Black typically settles for ...d6 and may build a Hedgehog formation, playing for patient counterplay against White's space advantage.