Van't Kruijs Opening: what should Black play?

In this position arising from the Van't Kruijs Opening, Black's primary recommendation is O-O, which secures king safety and completes kingside development. Chosen in 94.2% of recorded games (42K recorded), the move leads to a virtually balanced game with an engine evaluation of -0.06.

The Strategy Behind Castling

By executing O-O, Black tucks the king onto g8 while preparing central counterplay against White's setup. The computer main line continues with O-O Re1 d5 Bf1 c5 Nbd2, where Black immediately stakes a claim in the center with pawns on d5 and c5. Because White's bishop on c4 has already expended a tempo, Black can comfortably challenge the d4-pawn without tactical vulnerability on the a2–g8 diagonal.

Central Alternatives

Although castling is overwhelmingly preferred, other viable continuations exist. The direct pawn push d5 offers complete balance at a +0.00 evaluation and features in 1.5% of games (669 recorded), typically leading to d5 Be2 O-O b4 a5 b5. Additionally, developing the queenside knight via Nc6 appears in 2.8% of recorded games (1.2K recorded) with an evaluation of +0.12, followed in the engine ranking by Nc6 Re1 Bg4 Bb5 O-O Nbd2. Both setups remain sound, though they simply defer the natural relocation of the black king.

Flank and Bishop Continuations

Minor alternatives include a6 (1.5% of games, 662 recorded, evaluated at +0.17) and Bf5 (+0.21 eval). The line a6 Re1 O-O e4 c5 dxc5 grants Black an active stance against White's central space, while Bf5 Bd3 e6 c4 O-O Nc3 develops the light-squared bishop before committing pawns to light squares. Nevertheless, postponing O-O offers White slight initiative, explaining the immense master-level consensus behind immediate castling.