Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...Nf6/4. O-O/4...Bc5

A sideline in the Berlin defence where Black has developed their bishop to its most active square.

White can take the pawn, 5. Nxe5. Although the e5 pawn appears to be defended by Black's knight, the position of the bishop on c5 means that it is potentially forkable. Therefore, 5...Nxe5 is met with 6. d4, forking the bishop and knight. Nevertheless, Black can safely navigate this and eventually recover the pawn, though Black needs to be aware of the danger of Re1, exploiting the open e-file while their king is still in the centre (e.g. 6...Nxe4? 7. dxc5 Nxc5 8. Re1!).

5...Nxe4 first is also playable, where 6. Re1? is a mistake allowing 6...Bxf2+ forking the king and rook. After 6. Qe2 instead, leaving the rook to guard f2, one continuation is 6...Nxe5 7. Qxe4 Qe7 8. d4 Nc6 9. Qxe7+ Bxe7.

5. c3 preparing d4, is the most common continuation and more straight-forward than the complicated 5. Nxe5 lines. 5. c3 is called the Zukertort gambit: White is actually offering Black their e-pawn, 5...Nxe4, but they can recover it easily enough after 6. Qe2.

5. Re1?, though it seems natural, is a mistake due to the pressure the bishop is exerting on f2. After 5...Ng4, White will have to move their rook back again. (6. d4 is a nice try but insufficient. At best, 6...Nxd4 7. Be3 Nxe3 8. fxe3 Nxb5-+, Black is up a bishop and a pawn.)

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• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.