Berlin Defense, Beverwijk Variation

4...Bc5 skips the usual capture on e4 and develops the bishop to its most active diagonal, where it eyes f2. It is also reached from the Cordel Defense, 3...Bc5, when Black follows with ...Nf6. The bishop on c5 creates a tactical liability, because a white d-pawn advance can fork it with the knight on e5. The engine's top move is therefore 5. Nxe5, when 5...Nxe5 6. d4 regains the piece for White. Black can recover the pawn but must watch the e-file, as 6...Nxe4? 7. dxc5 Nxc5 8. Re1 shows. The alternative 5...Nxe4 punishes 6. Re1? with 6...Bxf2+, so White plays 6. Qe2, and 6...Nxe5 7. Qxe4 Qe7 8. d4 Nc6 9. Qxe7+ Bxe7 leads to a level, queenless position.

In practice 5. c3, the Zukertort Gambit, is the most common reply. It prepares d4 and offers e4, which White wins back after 5...Nxe4 6. Qe2. 5. Re1 is popular, though it is considered inaccurate because of 5...Ng4, which hits f2. The engine gives White a slight edge.